II. THE AGE OF THE FAUNA. (a) Summary of Previous Work.-In 1837, Hausmann recorded the occurrence of some shells obtained by Hertzog from strata in the Sunday's River district, to which he ascribed a Lower Cretaceous age. These included a Hamites, which was compared with H. intermedius J. Sow. and H. funatus Brongn., and a Trigonia which was thought to resemble T. dædalea Park.* Goldfuss afterwards described and figured two of Hausmann's shells under the names Lyrodon herzogi and Cytherea herzogi, and also considered them to be of Greensand age.† The examination of a small collection of lamellibranchs obtained by F. Krauss in 1839 from strata exposed on the Zwartkop's River, led that author to the conclusion that they indicated a Lower Greensand horizon, and in another paper Krauss furnished excellent descriptions and figures of these shells, maintaining a similar view concerning their age.§ In 1851 a collection of fossil plants and molluscs, obtained by R. Rubidge on the Sunday's River, was exhibited before the British Association at Ipswich by Colonel Portlock, who remarked that the shells were apparently of Jurassic age, while Dr. Harvey's examination of the plant remains was thought to corroborate this view.|| In his well-known paper published in 1856, A. G. Bain¶ referred the Uitenhage fossils with doubt to the Lias, basing this opinion upon the prevalence of a supposed Liassic form, "Gryphaa incurva.” The shell mistaken for this, however, was Exogyra imbricata, previously described by Krauss, which, as we shall see, bears only a superficial resemblance to the Gryphaa mentioned, and is in reality closely comparable with certain Lower Cretaceous forms of Exogyra. Appended to Bain's paper were D. Sharpe's descriptions of the Secondary fossils collected by Atherstone and Bain from localities on the Sunday's and Zwartkop's Rivers. The forms described, principally Mullusca, led Sharpe to the conclusion that they most nearly resembled European species of the Middle and Lower Oolites; he compared his Ammonites atherstoni with A. macrocephalus and A. herveyi, while believing Ammonites baini to be related to A. humphresianus and other Lower Oolitic forms. * Hausmann (1), p. 1457. † Goldfuss (1), Band II., p. 202, pl. 137, fig. 5 (1837); p. 239, pl. 149, fig. 10 (1840). Krauss (1), pp. 129, 130. || Portlock (1). § Krauss (2). In 1867, a paper by Ralph Tate, in which many new forms were described and figured, added largely to our knowledge of the Uitenhage fossils, and this author was led to some remarkable conclusions from his study of the fauna. He believed the assemblage to indicate a Jurassic age, and stated that he thought it to represent the fauna of the Oolitic rocks of Europe, and to approximate to that of the Great Oolite. It seems clear that in instituting this comparison, he made use of some molluscan types little adapted to serve the purposes of a critical correlation, and he was at the same time misled by several quite erroneous identifications. He also misunderstood the affinities of the cephalopods and the significance of certain Trigonia which alone might have been expected to form obstacles to his conclusions. It is here scarcely necessary to do more than refer to the curious generalisation arrived at by Tate concerning the relation of these supposed Jurassic deposits to the Jurassic strata of Europe, namely, that the "Oolites" of South Africa are the representatives of the whole of the Jurassic rocks of Europe with the exception of the Upper Oolites, and illustrate an intermingling of palæontological types which are analogous to, or identical with, those distributed in successive zones in Europe. In his monograph on the Cretaceous lamellibranchs of Southern India, Stoliczka made some reference to Uitenhage forms. He evidently believed Tate's Crassatella complicata to belong to the genus Ptychomya, and he ascribed Astarte herzogi Krauss to Speyer's genus Grotriania. He further expressed the opinion that Krauss's Astarte bronni might belong to the Cretaceous genus Remondia Gabb, and thought that in addition to these and Trigonia ventricosa, several other Uitenhage shells show a Cretaceous rather than a Jurassic aspect; attention was drawn to the great similarity between Trigonia ventricosa (Krauss) and the Cretaceous T. tuberculifera Stol., from Southern India. While we shall see that Stoliczka rightly recognised some of the Uitenhage forms to exhibit Cretaceous affinities, he was in error in ascribing Astarte herzogi to the genus Grotriania, and, as afterwards pointed out by Neumayr, wrongly supposed Astarte bronni to belong to the genus Remondia. A. bronni is so distinctly characterised that Neumayr proposed for it the new generic name Seebachia—a fact which appears to have been overlooked by Stanton, who in 1897 still tentatively included it in the genus Remondia.‡ One of Tate's Uitenhage species, the so-called Crassatella com* Tate (1). ↑ Stoliczka (2), pp. 286, 294, 315 (1871). Stanton (1). plicata, was later also recognised by Dames to be a representative of the genus Ptychomya,* and this seemed to point to a later age for the strata from which it was obtained than that assigned by Tate. Dames was further led to the belief in the Neocomian age of the Uitenhage beds by a fragment of an ammonite (sent by Krauss to L. von Buch) which he thought to be identical with Ammonites astierianus d'Orb. In the concluding chapter of his monograph on the British Fossil Trigonia, Lycett† referred briefly to the Trigonia of the Uitenhage Formation, and expressed his opinion that some of the most characteristic of these point decisively to a Cretaceous age; he also showed that the alleged occurrence of T. goldfussi, which Tate had used as evidence for a Jurassic age, rested on an erroneous determination. The whole question of the age of this fauna was afterwards well handled by Neumayr, who subjected Tate's work to some criticism. Neumayr set on one side many molluscan types as of little significance in a comparative study, and concluded that a costate Trigonia (T. tatei Neum.) alone exhibited a marked Jurassic character. On the other hand, he considered a number of forms to represent essentially Cretaceous types. Such were Holcostephanus atherstoni (Sharpe); Holcostephanus baini (Sharpe); Crioceras spinosissimum (Hausm.) Neumayr; Trigonia ventricosa (Krauss); Trigonia conocardiiformis (Krauss); Ptychomya complicata (Tate)§; and Exogyra imbricata Krauss. He suggested that Tate's Ammonites subanceps, which was thought by Tate to resemble the Jurassic A. anceps Rein., might really represent the young of Crioceras spinosissimum. It was admitted by Neumayr that Belemnites africanus Tate, which Tate placed in the group Canaliculati and considered to afford strong evidence for an Oolitic age, bears a strong resemblance to the Jurassic forms B. canaliculatus Schloth. and B. magnificus d'Orb.; but at the same time he drew attention to the existence of a belemnite in the Lower Cretaceous of North Germany which seemed to share some of the characteristics of B. africanus. In a later paper, written after an examination of Tate's original specimen in the collection of the Geological Society, Neumayr || definitely separated B. africanus from the Canaliculati, and included it in his group of the Absoluti, which, as he remarked, extend in their occurrence up to the Aptian; hence the conclusive nature of the * Dames (1). Holub and Neumayr (1). || Neumayr (4). + Lycett (3), p. 230 (1879). § Misquoted "implicata " by Neumayr. evidence for age furnished by the occurrence of B. africanus in the Uitenhage beds was no longer to be recognised.* Neumayr's argument for the Lower Cretaceous age of this fauna appears indeed to be overwhelmingly strong, particularly in the evidence of the Cephalopoda, all of which he found to possess near allies in European Neocomian forms. Regarding the two species of Holcostephanus, Neumayr pointed out that their resemblance to the Jurassic types with which they had previously been brought into comparison was only of a superficial character, depending alone on a certain outward similarity of habit. Pavlow has since confirmed this view, after studying South African specimens, and has placed Holcostephanus atherstoni and H. baini in his generic or sub-generic division Astieria, which comprises numerous Neocomian types; he even goes so far as to identify Holcostephanus atherstoni with H. psilostomus Neum. and Uhlig, from the Hilsthon of North Germany, and to the same form he ascribes a shell from the Neocomian of Speeton. In view of the fact that the plant remains found in the Uitenhage beds had previously been thought to point rather to an Oolitic than a Cretaceous age, and having regard to the division of opinion concerning the affinities of the invertebrate fauna, Messrs. Rogers and Schwarz, in 1901, were led to adopt the provisional conclusion that the Uitenhage Series may be assigned to the Upper Jurassic.§ In stating this, they mention that the fauna and flora have been considered to resemble in some degree those of the Jurassic series in Cutch. It is well known that the resemblance between certain lamellibranchs of the Uitenhage beds and those of the Oomia Group in Cutch has been frequently remarked upon, but it can no longer be maintained that the marine Oomia strata are in reality of Jurassic age, at least so far as concerns the Trigonia-beds; but this is a point to which we may presently return, and one which we may consider in greater detail. In more recent works Mr. Rogers || gives us a comprehensive account of the Uitenhage Series, and now considers these beds to represent a portion of the Cretaceous system. The same view is adopted by Drs. Hatch and Corstorphine in their "Geology of South Africa" (1905). With reference to the flora, Prof. A. C. * See also Neumayr (5). + Pavlow and Lamplugh (1), pp. 492-497 (134-139 in authors' copy). Neumayr and Uhlig (1), p. 149, pl. xxxii., fig. 2. § Rogers and Schwarz (1), p. 17. || Rogers (1), pp. 281-318; Rogers (2), pp. 15-33, 45. Seward, in his memoir on the subject, has shown that the Uitenhage plants include types in part characteristic of Wealden and in part indicative of Jurassic floras"; but he believes that the balance of evidence derived from the plants is in favour of a Wealden age. We thus see that recent authoritative opinions have lent strong confirmation to the views of the earliest writers who made a study of this fauna. Other works in which less critical reference has been made to the age of the Uitenhage Series may now be briefly noticed. In 1857, W. G. Atherstone suggested the partly Jurassic and partly Cretaceous age of the Uitenhage beds, but Andrew Wyley, in 1859, placed the Enon Beds so low as the New Red Sandstone, and correlated the Sunday's River Beds with the Jurassic (Oolites).‡ Feistmantel § evidently shared Tate's view of an Oolitic age when he tried to show affinities between certain Mollusca from the Uitenhage beds and others from the Oomia Group in Cutch in order to prove the Lower Oolitic age of the Oomia fauna and bring about harmony between the evidence for age furnished by the plants and animals from those beds. In a correlation of the Indian and African Mesozoic formations the same author also tabulated the Uitenhage Series as Jurassic.|| G. W. Stow divided the formation into a "Lower Jurassic" and an "Upper Jurassic" series. In 1878 W. T. Blanford, basing his view upon a study of Tate's and Stow's papers, concluded that the beds containing Hamites yielded too large a number of Middle Jurassic forms for reference to the Neocomian; but he believed them to represent a very high Jurassic horizon, while pointing out that Trigonia ventricosa and T. vau were still higher.** In 1880 Griesbach classed the Uitenhage beds as Jurassic, tt while the same view was adopted by T. Rupert Jones in 1884‡‡ and by Moulle in the following year. §§ Even so recently as 1897, Futterer has accepted Sharpe's and Tate's conclusions. || || On the other hand, Gürich,¶¶ Schenck,*** and Molengraaff††† have referred these beds * Seward (1), p. 46. † Atherstone (1), pp. 584, 588. Wyley (1). [I have not seen Wyley's Report, but his correlation is set forth in Tate (1), p. 172, and Corstorphine (1), Appendix.] § Feistmantel (1). ¶ Stow (1). tt Griesbach (1), pp. 90, 93. Moulle (1), p. 216. ¶¶ Gürich (1). || Feistmantel (4), pp. 54, 59, 84. Jones (1); Jones (2), p. 737. Schenck (1), p. 231. ttt Molengraaff (1). [I have not been able to see this work, but quote the statement and reference on the authority of Newton (2), p. 146.] |