Still greater interest attaches to a Trigonia which strongly recalls the peculiar types belonging to the group of T. v-scripta in the Oomia Trigonia beds and the Uitenhage group of T. vau. This is T. kühni Müll., found in strata ascribed to the Upper Neocomian at a locality 23 km. west-south-west of Mtshinga, and it possesses characters which appear to indicate relationship to one of the groups. mentioned rather than to the members of other groups with which Dr. Müller has also brought it into comparison. Trigonia kühni, it is true, seems to be distinguished from T. vau as well as from T. v-scripta and its allies both by its less equilateral form and the persistent ornaments of its escutcheon; but to judge from the description, and especially from the figure of an imperfect specimen* which shows the convexity of the anterior profile and the crowded ribs of the frontal series obliquely crossing the growth lines-just as in the Oomia T. recurva-there can be little doubt about the position of this shell relative to the main divisions of the genus. Whether it is more closely allied to the group of T. v-scripta or to T. vau and T. stowi sp. nov., cannot be ascertained until more perfect specimens can be obtained and the sculpture of the youthful growth-stage examined.

Of less significance, perhaps, is the occurrence of Pecten striatopunctatus Roem., which was found with Gervillia dentata, and Arca uitenhagensis Müller, which accompanies Trigonia beyschlagi. They may be brought into near comparison with Pecten projectus Tate and Arca jonesi Tate, though little importance could be attached to such types as these, if taken alone. Another Pecten, from the same locality as that from which P. striato-punctatus was obtained, was considered by Müller to represent very probably P. cottaldinus d'Orb., which also occurs in the Uitenhage beds. The relationship of the Oomia fauna to that described from German East Africa is of course what we might expect to find, having regard to the manner in which a close connection between the Upper Jurassic faunas of East Africa and Cutch has been demonstrated by those who have studied the Cephalopoda.

Enough has been said to indicate the position taken by these East African occurrences in a widely distributed Neocomian fauna of southern type, and to show that such connecting links as are available, no less than the general aspect which the fauna, wherever it is developed, derives from the prevalence of peculiarly characterised Trigonia, plainly serve to unite the molluscan assemblages of these three remotely separated districts in the eastern hemisphere. * G. Müller (1), Taf. xxv., fig. 8.

Some indications of a western extension of the same type of fauna are to be recognised on the South American continent.

*

(e) Neocomian in South America.-Amongst the fossils collected in 1899 by the late J. B. Hatcher from the Pueyrrydon Series in Patagonia are several lamellibranchs of distinctive type which permit of close comparison with some of those above discussed. They have been described and figured by Stanton, who was led to ascribe a Lower Cretaceous age to the Pueyrrydon Series, though he was unable to establish a narrower correlation with the formations of other regions. The most striking resemblances to Uitenhage forms are seen in two Trigonia from the Belgrano beds, T. subventricosa Stanton, a member of the section Scabræ, and T. heterosculpta Stanton, believed by Stanton to be allied to T. vau Sharpe. Trigonia subventricosa certainly approaches very closely to T. ventricosa, particularly in the wide spacing and robustness of the anterior varices. The differences in the sculpture pointed out by Dr. Stanton appear to be less emphasised when this Patagonian form is brought into comparison with the large and more coarsely ornamented T. kraussi sp. nov., which occurs with T. ventricosa. But if the relations of height to length exhibited by the figured specimen of T. subventricosa be those which characterise the average shells of that form, then there is good ground for the separation of these three members of the Scabræ, which at the same time appear to be united by similar broad features of peculiar form and ornament. They are the only known examples of this particular extreme type, and probably represent a group in this southern developmen parallel with that of which T. scabricola Lycett and T. aliformis Park. are typical members in Europe.

The ornamentation of T. heterosculpta is of such a kind as to recall instantly the conspicuous shells of the groups of T. v-scripta and T. vau. The principal points of resemblance are the manner in which steeply inclined ribs of two series on the flank meet to form an angular pattern, and the absence of sculpture from the area and the posterior portion of the flank in the adult shell. T. heterosculpta is certainly not to be brought into comparison with the European Undulatæ, but its whole aspect suggests a close connection with the group of T. vau. Its near relationship to T. vau and T. stowi is clearly to be inferred from a comparison of the youthful characters, which are very similar, and affinity with these rather than with the Indian group of T. v-scripta is exactly what we might expect to find, having regard to the geographical relationships. The adult * Hatcher (1). + Stanton (3).

T. heterosculpta differs, however, from its African allies by the less. posterior elongation of the shell.

Here again, in the Belgrano beds, we find an associated Gervillia of large dimensions, which does not appear to be widely removed from G. dentata Krauss, while a large Astarte (A. perlata Stanton) with short and deeply excavated lunule, may be said to have its parallel in the Oomia beds of Cutch, if we confine the comparison to broad outward features. At a somewhat lower horizon in the Pueyrrydon Series (the Gio beds) Ostrea tardensis Stanton, which occurs abundantly, represents a type of Ostrea or Exogyra which has much in common with Exogyra imbricata Krauss; and to judge from the description of O. tardensis, it seems likely that these two forms may really be very closely comparable. A special value cannot, of course, be attached to the comparison of such types as these if studied alone, but the resemblance gains significance when viewed in connection with the other Mollusca above discussed. It will be seen therefore, that although the basis of comparison is somewhat slender, yet the occurrences above noted in no slight measure suggest the closest alliance with the molluscan fauna of the South African Neocomian; and it may be added that there is nothing in the Pueyrrydon fauna itself to contradict the assumption that wer are dealing with a western part-equivalent of the Uitenhage development.

A search for further traces of the characterising elements of the Uitenhage fauna in the Lower Cretaceous deposits of South America reveals evidences of a very suggestive description. The Lower Cretaceous beds in Bolivia and Chili which have yielded Trigonia transitoria Steinmann * are probably of similar age and seem to represent the more northerly equivalents or part-equivalents of the Pueyrrydon Series. Trigonia transitoria has also been found to occur abundantly at the Arroyo Triuguico and at Quili Malal in the Argentine Republic, in strata ascribed by Behrendsent to the Neocomian. It occurs, moreover, with significant associates in the Trigonia-beds of Lower Neocomian age exposed on the left bank of the Rio Agrio, opposite to Las Lajas (Argentine Republic); ‡ these beds yield another member of the Pseudo-quadratæ (T. neuquensis Burckhardt) and a Trigonia very closely resembling the South African T. conocardiiformis, § as well as an Eriphyla in some respects comparable with the South African Astarte (Eryphyla) * Steinmann (1), p. 260; Steinmann (3); R. A. Philippi (1), p. 63; Paulcke (1), p. 297. + Behrendsen (1), p. 25.

Burckhardt (1), p. 21.

§ Burckhardt (2), pp. 72-75, 111, 112.

herzogi. Dr. Stanton has suggested that a Trigonia quoted by Behrendsen as "Trigonia cf. aliformis Park." from supposed Upper Neocomian beds at the Arroyo Pequenco may possibly be identical with the Patagonian T. subventricosa. It is accompanied by an oyster which Behrendsen identified with Exogyra couloni, and found to agree well with the figures of Ostrea couloni cited by Bayle and Coquandt from the Neocomian at Arqueros in Chili. The Chilian shells ascribed to O. couloni bear a considerable resemblance to the Uitenhage Exogyra imbricata Krauss, with which Coquand even later identified them, and accompanying this oyster in Chili is Trigonia delafossei Bayle and Coquand, the resemblance of which to T. ventricosa has been elsewhere remarked upon.§ Associated with these forms is a Crioceras identified by Bayle and Coquand with the European C. duvali Lév., thus recalling the analogous association of Trigonia ventricosa, Crioceras spinosissimum and Exogyra imbricata in South Africa. Of the above-mentioned Mollusca, Trigonia delafossei, T. transitoria, T. neuquensis, and T. cf. conocardiiformis suggest very strongly their relationship to Uitenhage and Oomia forms. It should be noted also that Philippi has described Trigonie from localities in Chili, which share the characters of peculiar sculpture and siphonal elongation shown by the group of T. vau Sharpe, while T. eximia R. A. Philippi, from the Tinguirica valley in Chili, appears to be closely related to T. conocardiiformis (Krauss) and Burckhardt's T. cf. conocardiiformis.

IV. THE DISTRIBUTION OF THE UITENHAGE FAUNA IN RELATION TO SOME THEORETICAL QUESTIONS.

We may now briefly consider in what measure the correlation of the Uitenhage Neocomian fauna with the similar assemblages in German East Africa and in Cutch bears upon the theory of an IndoAfrican land barrier during early Cretaceous times; and further, we may inquire how far the facts concerning the dispersal of these Mollusca have significance in relation to Neumayr's theory of distribution according to climatic zones, as deduced from a study of the Cephalopoda. The one question is in reality largely bound up with the other, and since in both cases the inquiry is of a so purely palæontological character, it may be of advantage briefly to review the evidence now available. Moreover, it is advisable to glance at

* Behrendsen (1), p. 418. Coquand (2), p. 158.

Bayle and Coquand (1), p. 37.

§ Lycett (3), p. 120 (1875); Kitchin (1), p. 108; Paulcke (1), p. 296.

these aspects of the distribution as now known to us, because Neumayr himself attached very great importance to the testimony of the Uitenhage fauna in supporting both the above theories. But at that time it was not known that the links connecting the bivalvefaunas of the Uitenhage and Oomia strata were so numerous or complete as they are now proved to be, while the existence of a related molluscan assemblage in German East Africa was unsuspected.

Although Neumayr was led to the theory of a great equatorial enclosed sea (" Ethiopian Mediterranean ") chiefly by a comparative study of faunas of essentially Jurassic character, yet he felt justified in utilising the Uitenhage fauna also as an aid in this palæogeographic reconstruction.* He believed that the radical differences between the Mollusca of these beds and the more northerly East African occurrences of Upper Jurassic age were an indication that the faunas had for some time lived in distinct areas separated by a land barrier, and from this he thought to derive support for a theory the truth of which had seemed to be attested by evidence of a different character. † In spite of weighty opposition, this theory of a land connection extending from the Indian peninsula through Madagascar to South Africa at the beginning of Cretaceous times has continued to find favour, and it is only comparatively recently that the significance of the palæontological evidence has again been called in question. In view of the presence of some traces of the Uitenhage fauna in the Godavari district and also in Cutch and Hazara, Neumayr supposed that a connection between the equatorial and southern waters must have existed in the form of a strait, the situation of which he believed to be most probably about the present Gangetic plain. The late Dr. W. T. Blanford held a similar view; § he summarised the main arguments in favour of the theory, suggesting that a shallow water connection near India,- situated very possibly to the eastwards, though not precisely as Neumayr supposed,-would account for the northerly dispersal, and that if this were later converted into land, the "progressive diminution of European species in the three stages of the S. Indian Cretaceous. beds would be explained by the increasing effect of isolation." Professor Suess also speaks of these traces of the Uitenhage fauna. in Cutch and in the Salt Range as possible indications of an

Neumayr (3); Neumayr (6), pp. 259, 261, 295, 296, 529.

Stow (1), p. 546; H. F. Blanford (1), pp. 534-540; Medlicott and Blanford (1), pp. xxxix., lxviii., lxxii., 297.

Wallace (1), pp. 422–427.

§ W. T. Blanford (3), pp. 98, 99.