MODIOLA LATA. 65 



appears so very distinct a form from M. Macadamii, I am disposed to think that 

 they all merge one into the other ; but for the advantage of distinguishing the shell 

 in other localities I have separated this variety, so strongly marked, as a distinct 

 species." The figures given are all very good, and fortunately the original types are 

 all preserved in the museum of the Geological Survey, Jermyn Street. An 

 examination of M. suhparallela at once demonstrates the fact that this shell does 

 not belong to that genus, but from its general shape and contour closely resembles 

 Anthracomya (Salter), to Avhich genus I have referred the shell. Pal. Soc. ' Mono- 

 gra|)h on Carbonicola, Anthracomya, and Naidaites,' Appendix, p. 177, 1896. 



M'Coy described only one form as Modiola Macadamii, stating in his remarks, 

 " This is a very variable shell." Unfortunately no figures were given, but from the 

 description that the shell was " marked with rather distant, irregular, deep, concentric 

 striae," it is probable that he considered Portlock's var. elongata as the type, but 

 nothing is said on the subject ; and the form depicted by the terms "transversely 

 ovate, gibbous," can hardly be applied to the species under description, but he gives 

 M. angusta and M. suhparallela as distinct species. 



Modiola lata, Portlock, 1843. Plate II, figs. 23—27. 



MoDioiiA Macadamif, var. elongata, Porlloch, 1S43. Eeport Geology Loudon- 



deiTv, &c., p. 432, pi. xxxiv, fig. 14. 



— — var. LATA, Portlock, Ibid., fig. 15. 



— — M'Coy, 1844. Synopsis of the Characters o£ the Carb. 



Limestone Fossils of Ireland, p. 75. 

 — (pars). Brown. Fossil Conch., 1849, p. 175, pi. Ixi***, 



figs. 15 and 16. 



— — — var. ELONGATA, Etheridge, 1888. British Fossils, 



vol. i, Palseoz., p. 285. 



Specific Characters. — Shell transversely and obliquely ovate, moderately swollen, 

 especially in front. The anterior end is very short, regularly gibbose, and bluntly 

 rounded in front, Avith a narrow dorso-ventral diameter. The inferior border is almost 

 straight, and directed downwards and backwards, becoming bluntly rounded as it passes 

 into the posterior border, which is very obliquely truncate above but rounded below. 

 The hinge-line is straight, and equal in length to more than one-half the greatest 

 diameter of the shell. It forms with the posterior border a Viry obtuse angle, and is 

 raised behind. The umbones are anterior, blunt, but not terminal, remote from the 

 hinge-line, from which they are separated by a distinct fold, which is narrow 

 in front and becomes Avider behind. The shell is obliquely swollen, the swelling 

 becoming gradually expanded and flattened as it passes from before backwards, 

 the upper edge being acute for a short distance from the umbo ; above this 



9 



