TRIBE MYTILACEA. 239 
not cross each other: white, thin, fragile and scarcely pearly un- 
der a greenish brown epidermis. Peru and Chili in stones. Closely 
allied to the last. 
M. Lavicata. (not of Gray) Lirnopomus L. Quoy. Ast. t. 78. f. 
17, 8. Elongated subcylindrical straight, thin, smooth with a 
greenish brown epidermis ; a lateral oblique furrow ; within brown- 
ish white, pearly with a violet stain at the uncinated anterior extremi- 
ty.—In Madrepores.— New Guinea. 
M. Fusca.” Desh. in Lam. vol. 7. p. 28.—Myrtitus. F. W. t. 12. 
Ff. 12.—Gmel. 3359.—D. p. 306—Mopiota Cinnamonea. Var. 
Lam. 18.—List. t. 359. f.197. Small subcylindrical, much curved 
and finely striated; obtuse and heart shaped at the posterior extremity, 
rounded at the other ; the beaks recurved and slightly prominent ; 
white and thickish under a rich brown cuticle. 2—Jndian Ocean in 
Madrepores. Very like Cinnamonea. 
M. Truncata.—Lituopomus. T. Gray in App. to Dieffenbach. 
Zeal. Oblong, subcylindrical, thin; short and roundly truncated 
posteriorly, contracted in the middle, and tapering anteriorly; cuticle 
dark brown; umbones rather prominent, inflexed ; within purplish, 
nacreous. New Zealand. Easily recognized by its truncated ex- 
tremity, and prominent umbones. The front portion is usually covered 
with regular green lamine which are perhaps Alge. 
M. Orirex. Say. Jour. A. N. S. Philad. 2. p. 369. t. 19. f. 2. 
Oval, reddish brown, ventral edge slightly contracted behind the 
middle, from which spot to the beaks the surface is blackish and 
transversely wrinkled ; sides longitudinally striated, except the an- 
terior cordate hinge margin, which is flattened and covered with a 
stratum of compact sand :. anterior tip equally arcuated above and 
below: irridescent within. 0,23..0, 47.—Minorca. 
M. Canatirera.—Litnopomus C. Nobis Zool P. 1844. Sub- 
cylindrical, rather elongated, subarcuated, covered with a smooth 
rufous or reddish yellow epidermis, which is concealed by a calca- 
reous coating, which on the umbonal slope assumes the appearance 
of four slightly elevated radiating walls roofed by another layer of 
calcareous matter, and terminating in three narrow channel-like 
apertures at the anterior extremity : posterior end rounded, anterior 
extremity attenuated and obtuse: dorsal and ventral edges sub- 
parallel, the former incurved, the latter slightly convex: anterior 
surface divided by an oblique furrow from the more elevated pos- 
terior, 3$..13.—S. America. 
M. Prumvuta.—Lirxopomus P. Nobis Zool. P. 1844, Extremely 
like the last, but the anterior extremity less obtuse, and the calca- 
reous cellular coating of the umbonal ridge, resembling a ruffled 
feather in its arrangement, being composed of elevated thin ridges 
which slope anteriorly and diverge from their point of junction, 
