THE BRITISH FOSSIL BRACHIOPODA. 245 



4. Terebratulina triangularis, Etheridge. Dav., Appendix to Supplements, Vol. V, 



PL XVIII, figs. 3, 3 «, b. 



Terebratula striata, var. triangularis, Etheridge. Appendix to W. H. Penning 



and Jukes-Brown's Memoir on the Geology of 

 the Neighbourhood of Cambridge, p. 148, 

 pi. iii, fig. 15, 1881. 



Shell small, somewhat triangular, anteriorly broadly rounded, tapering posteriorly; 

 hinge-line less than half the breadth of the shell ; dorsal valve very moderately convex, 

 sometimes more or less flattened, and slightly depressed along the middle ; auricles on 

 either side of the umbonal beak well defined. Ventral valve more convex and deeper than 

 the opposite one ; beak very little incurved ; foramen comparatively large ; deltidial plates 

 small ; beak-ridges well defined, and leaving between them and the hinge-line a small 

 flattened space. Surface of valves covered with a variable number of radiating ribs, with 

 one or two shorter riblets interpolated between the longer ones. Surface of valves 

 crossed by concentric lines of growth. 



Length and breadth 3, depth \\ lines. 



Obs. — This is the shell that occurs by thousands in the Upper Greensand in the 

 neighbourhood of Cambridge, and to which the name of T. rigida has been sometimes 

 applied. It is described by Etheridge as a variety of Terebratulina striata, but I differ 

 with my friend in this particular, and believe it more nearly allied to Terebratulina gracilis 

 than to T striata. It seems to be a well-marked species. If the name of triangularis 

 has not already been applied to some other species of the genus, I would gladly adopt it 

 for the little Upper- Greensand shell as something definite. 



Unfortunately the plates and figures of Brachiopoda in the Appendix to the ' Geology of 

 the Neighbourhood of Cambridge ' are so indefinite or badly drawn that they are useless 

 for purposes of identification, so that I have figured this shell after Mr. Etheridge's 

 specimen, kindly lent me for this purpose, out of the Museum of Practical Geology. I 

 question whether Mr. Etheridge's Terebratulina gracilis, var. nodulosa, is specifically 

 separable from the shell under description. 



5. Terebratella Keepingii, Walker, MS. Dav., Appendix to Supplements, PL 



XVIII, figs. 4, 4a, 5. 



Terebratella Keepingii (Walker), W. Keeping. The Fossils and palaeontological 



affinities of the Neocomian De- 

 posits of Upware and Brickhill, 

 Cambridge, p. I30,pl. vii, fig. 19, 

 1883. 



