CRISINA CENOMANA, d'Orbigny.

Plate I., fig. 5.

1851. Crisina cenomana, d'Orbigny, Bry. Crét., p. 732, pl. 614, figs. 1-5.

1845. Idmonea disticha, Michelin, Icon. Zooph., p. 204, pl. lii.,

fig. 18.

1853. Idmonea calypso, d'Orbigny, Bry. Crét., p. 733, pl. 747, figs. 10-14.

1890. Idmonea cenomana, Pergens, Revision des Bry. Crét. fig. par d'Orbigny, p. 344, pl. xii., fig. 3.

Zoarium subcylindrical, and the reverse face is convex or flat; there is no keel on the obverse face; the zoœcia are immersed, and when the reverse face is flat the zoœcial boundaries are clearly marked; the lateral series of apertures are quite regular, and just reach the middle line of the obverse face; there are about four apertures in each lateral series; the apertures are circular, all of one size; those of the same series are distant less than one diameter of an aperture; those of different series two or three diameters of an aperture.

This definition distinguishes C. cenomana from all cretaceous forms of Retecava as well as from others of Crisina. Those species of Retecava which most resemble it have a very slight median keel on the obverse face, except R. Abbotti (Gabb and Horn), (Journ. Acad. Nat. Sci. Philadelphia, ser. ii., vol. iv., 1860, p. 404, pl. lxix., figs. 45-47), but in this form there is a ridge down the obverse face of each zoœcium.

Two distinct forms are included under the above definition, and both occur in the material here described. In the first, resembling d'Orbigny's figure of C. cenomana, the zoœcial boundaries are hardly visible and the reverse face is convex. In the second (pl. xlv., fig. 4), resembling d'Orbigny's figure of Idmonea calypso, the zoœcial boundaries are strongly marked and the reverse face is flat. The only justification for placing the two forms under one name is their identification by Pergens.* Speaking of C. cenomana, under the synonyms of which he had placed I. calypso, Pergens says, "quelquefois les branches sont aplaties à la partie inférieure et forment ainsi une variété décrite comme I. calypso." That is, I. calypso is an earlier growth stage of C. cenomana confined to the proximal portions of the zoarium. In view of the very fragmentary character of the specimens usually obtained of these erect Idmoneids, * E, Pergens, Revision des Bry. Crét. fig. par d'Orbigny, 1890, p. 344.

it is exceedingly rare to get knowledge of the growth stages of any one form. But the specimens of C. cenomana here described do not look like proximal ends of zoaria. It is likely, then, that a form exists whose adult zoarium over its greater extent has the characters of I. calypso, d'Orbigny, while these are confined to the proximal parts of an adult zoarium of C. cenomana.

Distribution of both C. cenomana and I. calypso. Cenomanian.

CRISINA EXCAVATA (d'Orbigny).

Plate I., fig. 6.

1853. Idmonea excavata, d'Orbigny, Bry. Crét., p. 742, pl. 749, figs. 11-15.

Zoarium subtriangular with a flat or concave reverse face; the lateral series are regular and contain six to eight apertures; the apertures are circular; the zoœcia are emergent. Idmonea filiformis, d'Orbigny (Bry. Crét., 1853, p. 744, pl. 750, figs. 1-5), and Idmonea lata, d'Orbigny (Bry. Crét., 1853, p. 734, pl. 748, figs. 6-10) resemble this form, but have only three apertures in a lateral series. Idmonea marginata, d'Orbigny (Bry. Crét., 1853, p. 744, pl. 749, figs. 20-23), with which Gregory unites this form, differs from it by having immersed zoœcia.

Distribution. Senonian.

CRISINA MARGINATA (d'Orbigny).
Plate I., fig. 7.

1853. Idmonea marginata, d'Orbigny, Bry. Crét., p. 744, pl. 749, figs. 20-23.

1853. Idmonea angulosa, d'Orbigny, Bry. Crét., p. 735, pl. 748, figs. 11-15.

Zoarium subtriangular with a flat or convex reverse face; the lateral series are regular and each contains four or five apertures; the apertures are circular. This form is very like C. excavata (d'Orbigny), but has fewer apertures in a lateral series, and the zoœcia are immersed.

Distribution. Turonian and Senonian.

GENUS TERVIA, Jullien.

Idmoneida whose zoarium is erect and consists of solid branches. There is an unpaired median series of apertures between the two rows of simple lateral series. Terria is considered by Gregory as a

subgenus of Crisina, from which it differs in possessing a simple median series of apertures on the obverse face. The fact that it is not always easy to distinguish this series as composed of apertures distinct from the most median apertures of the lateral series shows the artificiality of the genus. This point is well exemplified in von Hagenow's figure of T. dorsata (von Hagenow).

TERVIA DORSATA (von Hagenow).

Plate I., fig. 8.

1851. Idmonea dorsata, von. Hagenow, Bry. Maastr. kr., p. 31, pl. ii., fig. 10.

Zoarium subcylindrical or triangular or flattened in a plane parallel to the obverse and reverse faces; without dorsal processes; reverse face flat or concave; zoœcia three or four in a lateral series, immersed but the boundaries are clearly marked; the distance between the different series of apertures is one and a half to two and a half times the diameter of an aperture; those of the same series are distant about a quarter the diameter of an aperture. This is the commonest form among the specimens of Cyclostomes from Need's Camp.

Distribution. Senonian.

TERVIA GIBBERA, Gregory.
Plate I., fig. 9.

1899. Crisina (Tervia) gibbera, Gregory, Brit. Mus. Cat. Cret. Bry., vol. i., pp. 173-4, Text fig. 12.

Zoarium subcylindrical with the reverse face flat and possessing spine-like projections, bearing no zoœcia, termed by Gregory "dorsal processes"; zoccia about three in a lateral series, immersed, but the boundaries are just shown; distance between the different series of apertures three to four times the diameter of an aperture; those of the same series distant about one-half the diameter of an aperture. Only two specimens have been found among the material here described.

Distribution. Senonian.

TERVIA DECURRENS (Pocta).

1892. Idmonea decurrens, Pocta, Mech. koryc. Hory.; Ceska. Ak. Fr. Jos. Pratze, sect. 2, p. 18, pl. ii., figs. 3–6.

Zoarium subtriangular in cross-section and flat on the reverse side; the zoœcia are immersed with their boundaries apparent; apertures

two or three in a lateral series; those of different series distant four or five diameters of an aperture, those of the same series two to three diameters of an aperture.

A single specimen is somewhat doubtfully referred to this species. It is the proximal end of a zoarium, though the first few zoocia appear to be missing. Beginning as a thin, cylindrical branch, the zoarium rapidly widens and becomes compressed in a plane parallel to the obverse and reverse faces, at the same time becoming very curved, so that in a section along the proximal-distal axis the obverse face appears convex and the reverse face concave. When the breadth of the zoarium has reached about one-third of its length, it divides into two subcylindrical branches; one of these is broken off short, but the other continues for about 1.5 mm., without altering in shape. It would be interesting to know if on further growth the branches flatten and widen, thus recapitulating the growth stages of the first part of the zoarium;* or whether the first part is really an encrusting portion, whose support has decayed, which has thrown up cylindrical branches in the same way as a Phalangella-like base has been shown by Gregory t to throw up branches of the genus Crisina. The general zoœcial characters are those of Tervia decurrens (Pocta), in which species it is provisionally placed.

1840. Ceriopora virgula, von Hagenow, Mon. Rüg.: Neu. Jahrb., 1840, p. 646.

1851. Pustulipora virgula, von Hagenow, Bry. Maastr. kreide., p. 17, pl. i., fig. 3.

Zoarium consisting of smooth cylindrical branches; the apertures are irregularly distributed on the zoarium and are very far apart, their distance apart in a proximal-distal direction being generally more than four times the diameter of an aperture. There are never more than two apertures in the breadth of a branch. The zoœcia

* See W. D. Lang, Geol. Mag., 1905, pp. 259-260.

J. W. Gregory, Brit. Mus. Cat. Cret. Bry., vol. i., 1899, p. 159, text-fig. 11,

are immersed. Entalophora Pergensi, Gregory,* which the above definition would also include, has thinner branches and the apertures still further apart than in E. virgula.

This is the commonest species of Cretaceous Entalophora and has been found in most of the localities whence Cretaceous Polyzoa have been recorded; but only one specimen has been found among the material here described.

Distribution. Neocomian-Danian.

ENTALOPHORA CONJUGATA, von Reuss.
Plate I., fig. 11.

1872-3. Entalophora conjugata, von Reuss, Bry. unt. Quad. Palæontogr., vol. xx., part. i., p. 117, pl. xxix., fig. 8.

Zoarium consisting of cylindrical branches; the apertures are distant from one another in a proximal-distal direction more than four times the diameter of an aperture; the apertures occur in rows of two or three across the branch; the zoœecia are immersed and their boundaries may be faintly marked. This form is very like E. geminata (von Hagenow), but the zoocia are shorter, the boundaries of the zoœecia are less clearly marked, and the apertures occur in groups of three instead of two as in E. geminata. A single specimen of this species occurs among the material here described. Distribution. Cenomanian.

ENTALOPHORA ECHINATA (Römer).
Plate I., fig. 12.

1840. Pustulopora echinata, Römer, Verst. Nordd. kr., p. 22, pl. v., fig. 23.

1846. Pustulopora echinata, von. Reuss., Verst. Böhm kr., p. 64, pl. xiv., fig. 4.

Zoarium consisting of cylindrical branches; the apertures are distant from one another in a proximal-distal direction about four diameters of an aperture. There are about four apertures in the breadth of a branch; the diameter of the apertures is about 2 mm.; the zoœcia are immersed, with their boundaries more or less apparent. This species is very nearly allied to E. madreporacea (Goldfuss), from which it differs in having the apertures slightly further apart in a proximal-distal direction, the zoocial boundaries more prominent,

* J. W. Gregory, Brit. Mus. Cat. Cret. Bry., vol. i., 1899, p. 226, pl. x., figs. 5, 6, 7.

† Pustulipora geminata, von Hagenow, Bry. Maas. kr., 1851, pl. i., fig. 11, p. 20,