132 CARB0N1C0LA, ANTHRACOMYA, AND NAIADITES. 



Mytilus Wesemaelianus, de Byckholt. Melanges paleontologiques ; Mem. 



Coiironn. Acad. Roy. Belg., vol. xxiv, 

 1852, p. 140, pi. viii, figs. 11, 12. 

 Modiola Wtomingensis, Lea. Journ. Acad. Nat. Sci. Philad., new ser., vol. ii, 



pt. 3, p. 203, pi. xx, fig. 1 a, 1853. 

 Deeissenia laciniosa, B. Ludwig. Palaontograpbica, vol. viii, p. 38, pi. v, 



figs. 15, 19, 1859. 



— inflata, B. Ludwig. Ibid., vol. viii, p. 190, pi. Ixxi, figs. 8 — 10,1861. 

 dilatata (pars), B. Ludwig. Ibid., p. 189, pi. Ixxi, figs. 5 — 7. 



Mtalina modiolaris, Salter. Geol. tturv. Mem., ' Iron Ores of Soutb Wales,' 



p. 228, pi. ii, fig. 14, 1861. 

 Antheacomta 1 modiolaris, Salter. Ibid., p. 230, pi. ii, fig. 14. 



— — Ward. Trans. Nortb Staff. Inst. Min. and Mecb. 



Eugin., vol. x, 1890, p. 125, pi. i, fig. 13, 

 1890. 

 Anthracoptera modiolaris, Hind. Quart. Journ. Greol. Soc., vol. xlix, p. 251, 



vol. vii, figs. 1, 1 a, 1 b, 3—6, 1893. 



Specific Characters. — Shell obliquely elongated, compressed posteriorly. The 

 hinge-line is straight, nearly or quite as long as the greatest length of the shell. 



The anterior part of the shell is represented by a small gibbose lobe, which 

 projects forwards with a rounded border, which becomes concave below, and is 

 pierced by the byssus. The posterior part forms the greater portion of the shell ; 

 it is produced downwards and backwards, expanded, and gradually compressed into 

 the margin. The posterior border is bluntly curved, but it may be straight or 

 even emarginate, and meets the hinge-line at an angle which is either greater than 

 or equal to a right angle. The junction of the inferior and posterior borders is 

 bluntly curved. The umbones are anterior, not quite terminal, and on reaching 

 the hinge-line are curved forwards and inwards, not contiguous, slightly elevated 

 above the hinge-line. An acute and prominently swollen ridge, flatter in young 

 specimens, passes obliquely backwards and downwards, and, while preserving its 

 character in the anterior two-thirds, rapidly becomes lost in the lower and poste- 

 rior third. Anterior to this oblique ridge the shell is markedly constricted, often 

 becoming slightly concave. The ridge is bent forwards in front, and is parallel to 

 the hinge-line. It is much more pronounced in the left valve. The right valve is 

 much flattened. 



Interior, — The anterior muscle-sc;n\s arc three in number, pit-like; the anterior 

 markedly the largest, and situated within the umbo; the next is situated 

 just, below the horizontal part of the ridge (in casts), while the posterior scar 

 is on the fight exactly at the point where its direction becomes changed 

 downward. Tin; posterior scar is large and obovate, situated close to the 

 posterior superior angle of the shell. Faint traces of the attachment of byssal 

 muscles an; occasionally seen near \\\^ upper border. Two or three slight 



