﻿230 BRITISH FOSSIL TRIGONIvE. 



period, but was in some instances continued partially into the Molluscan fauna of the lower 

 portion of the Cretaceous rocks. Notwithstanding, however, certain specific resemblances, 

 I doubt the absolute identity of any one of these African species with European allied 

 forms. The occurrence of T. llerzoffii, Haussman, oiT. conocardiiformis, Krauss (p. 210), 

 and of T. ventricosa, Krauss (p. 119), in such profuse numbers and distributed over so 

 wide a region, the first a member of the Quadrata, the others of the Scahrce, may, in the 

 absence of reliable and guiding Ammonites, be regarded as affording strong, and to my 

 mind, decisive evidence of the Cretaceous character of the series. The resemblance 

 (perhaps even identity) of T. ventricosa with the Indian Cretaceous T. tuberctdifcra, Stol. 

 (' Mem. Gcol. Surv. India,' vol. iii, pi 1 5), tends materially to support the same conclusion. 



Two other Trigonia^, mentioned in Professor Tate's memoir, require notice. PI. 7, 

 fig. 6, of that memoir represents the magnified figure of a very young Trigonia, which is 

 attributed to T. Goldfmm, Ag. This, in common with other very young shells, might 

 possibly pertain to one of the QtiadratcB, and is even allied to certain young specimens of 

 T. dcedalea, Park. The other Trigonia mentioned is a single valve of one of the Costatce, 

 believed to represent a young specimen of T. Cassiope, d'Orb. (see PI. XXXII). 

 There can be no doubt of the importance which attaches to the presence of the Costatce 

 when the age of the stage is a question of doubt, but the presence of a single specimen 

 cannot be accepted as affording any decisive proof in such a question. 



The second, and apparently newer series of Cretaceous fossils, collected in the region 

 of the Umptafuna and Umzanbani rivers, contains T. clegans, Baily, a small and much 

 ornamented example of the Scabne (' Quart. Jour. Geol. Soc.,' vol. xi, plate 13, figs. 3 

 a, b). 



In Asia the Cretaceous Trigonige are scarcely known beyond the limits of the British 

 Indian Empire. In the southern region, near to Pondicherry, two short subglobose 

 species of the Glabra have been figured and described by Forbes (' Geol. Trans.,' 1846, 

 vol. vii, p. 150, pi. IS) nuder the names of 1\ scmiculta, T. orientalis, and T. sub- 

 orbicularis. The first of these species has the longitudinal costa; interrupted about the 

 middle of the shell by the usual smooth antecarinal space ; the other two, which I can 

 only regard as varieties of one species, have the costse, which are unusually prominent, 

 continued without interruption across the whole surface ; the area and escutcheon are 

 only slightly developed. The last-named form has the costse less prominent. They have 

 some general resemblance to the Glabra of the Jurassic Portland group, but differing in 

 having their costa? entirely devoid of tubercles. 



A small species of the Scabra, T. Forbesii (p. 122), is also distinct from European forms. 

 The Geological Survey of India has added but few additional Trigonia?. T. tuberculifera, 

 Stol., an inflated examj)le of the Aliformis group, presents in its surface-ornaments varied 

 aspects in its numerous specimens, which are altogether analogous to those assumed by 

 its near ally the T. ventricosa, Kr., of Southern Africa, a considerable and instructive 

 series of which are in the British Museum. Another small form of the Glabra, T. indicu. 



