MYTILUS. 9] 
Family—Myrition, Lamarek. 
Genus—Myritts, Linneus, 1758. 
(‘ Syst. Nat., ed. 10, p. 704.’) 
MYTILUS INRQUIVALVIS, Sowerby, 1836. Plate XV, figs. 7 a—d. 
1836. Myriztus InmQuivatvis, J. de C. Sowerby. Trans. Geol. Soc., ser. 2, vol. iv, 
pp. 241, 342, pl. xvii, fig. 16 (non Deshayes, 
1838). 
1854. = == J. Morris. Cat. Brit. Foss., ed. 2, p. 215. 
Description.—Shell slightly inequivalve, compressed, triangular, expanded and 
rounded posteriorly; edges sharp except at the anterior part of the ventral 
margin. Dorsal margin slightly curved, ventral nearly straight. Umbones slightly 
curved, pointed; no carina; greatest convexity between the umbones and the 
postero-ventral extremity. Surface smooth except for faintly marked growth- 
lines. 
Measurements : 
(1) (2) 
Umbo to postero-ventral extremity —. : 42 : 31mm. 
Height (at right angles to greatest length) . 24 : LOR 
Thickness ; . ; ; : ~. MBS F ia ees 
(1), the Type; (2), in the British Museum. 
Affinities—This species seems to approach M. Crallicnnei, d’Orbigny,! but is 
more compressed near the postero-ventral edge, less regular in outline, and without 
ornamentation near the ventral border. 
Type.—In the Bristol Museum. The only other specimen seen is in the British 
Museum. 
Distribution —Blackdown Greensand. 
Myritus, sp., ef. tornacensis, @’ Archiac, 1847. 
1847. Myrinus tornacensis, A. d’Archiac. Mém. Soc. géol. France, ser. 2 
vol. ii, p. 307, pl. xv, fig. 3. 
1847. — HAINOENSIS, P. de Ryckholt. Elucubrat. paléont. (not seen). 
i 1 «Pal. Franc. Terr. Crét.,’ vol. ii (1844), p. 273, pl. ceexxxix, figs. 1, 2. See also Geinitz, ‘‘ Das 
Elbthalgeb, in Sachsen” (‘ Paleontographica,’ vol. xx), pt. 1 (1873), p. 213, pl. xlviii, figs. 1—3, 
