120 CARBONICOLA, ANTHRACOMYA, AND NAIADITES. 



I noted in my first description that this shell somewhat resembled Anthracomi/a 

 lanceolata, PI. XV, fig. 11. It may be that this form stands in the same relation 

 to A. Williamsoni that the variety A. carinata does to A. minima ; and I am the 

 more inclined to think that this is the case, as I meet with an elongate form of 

 Anthracomya pulchra, PI. XV, fig. 29, and an elongate form of Anthracomya 

 Adamsii, PL XII, fig. 9, each occurring and only occurring in the same beds as the 

 normal variety, though this may not be true of A. Williamsoni and the form A. 

 lanceolata, as the actual horizon at which the latter occurs is at present uncertain. 



14. Anthkacomya Phillipsii. Plate XVI, figs. 10 — 16. 



Uicio Phillipsii, Williamson. Phil. Mag., vol. ix, p. 351, 1836. 

 Non — LiNGUiFOKHis, Phillips. Murchison's Sil. Syst., p. 88, 1839. 



Modiola, sp., Binney. Mem. Lit. Phil. Soc. Manchester, 2nd ser., vol. xii, p. 221, 



note, 1855. 

 Anthracomya Phillipsii, Huxley and Etheridge. Cat. Foss. Mus. Pract. G-eol., 



pp. 157—160, 1865. 

 — — T. Rupert Jones. Geol. Mag., vol. vii, p. 217, pi. ix, 



figs. 3 and 18, 1870. 

 R. Etheridge, jun. Ibid., ser. 2, vol. iv, pp. 243, 244, 



pi. xii, figs. 6 and 7, 1877. 

 Hind. Quart. Journ. Geol. Soc, vol. xlix, 1893, p. 262, 

 pi. ix, figs. 6, 6 a, 7, 8 ; pi. x, fig. 27. 



Specific Characters. — Shell transversely obliquely oval, modioliform, elongated 

 in a diagonal direction. The anterior end is small, its margin rounded. The 

 posterior end is compressed, expanded downwards and backwards, while above it 

 is rapidly compressed into the upper border, which is elevated posteriorly. The 

 hinge-line is straight, about one-half the length of the diagonal of the shell. The 

 ventral margin is convex, passing with a gentle curve into the anterior end, and 

 becoming straight shortly before it reaches the posterior end. The umbones are 

 anterior and directed forwards, very blunt and gibbose, the beaks themselves 

 inconspicuous. The shell itself is fairly tumid, and the valves are gibbose. There 

 is no sign of an oblique constriction anterior to the gibbosity, which is itself very 

 gradual in its form. Behind the gibbosity the valves are so rapidly compressed 

 as to become hollow on the posterior slope. 



Interior. — As far as can be seen in PI. XVI, fig. 14, which is a cast, the interior 

 is normal, but the anterior adductor scars are not seen, owing to damage to the 

 specimen. 



Exterior. — The surface is covered by fine and coarse striaa and lines of growth, 

 which have the general arrangement which obtains in this genus. Periostracum 

 thick and wrinkled. 



