150 ANATINIDA. 
Disir.—87 sp. India, Philippines, New Zealand, Japan, 
United States. Fossil, 50 sp. Devonian ’?—Oolite—; United 
States, Kurope. A. truncata, Lam. (eviii, 71). 
Shell oblong, ventricose, subequivalve, thin and translucent, 
posterior side attenuated and gaping; umbones fissured, directed 
backwards, supported internally by an oblique plate ; hinge 
with a spoon-shaped cartilage-process in each valve, furnished 
in front with a tranverse ossicle ; pallial sinus wide and shallow. 
Animal with a closed mantle and long united siphons, clothed 
with wrinkled epidermis; gills one on each side, thick, deeply 
plaited; palpi very long and narrow; pedal opening minute, 
foot very small, compressed. 
PLATYMYA, Agassiz, 1838. Some of the species of this fossil 
group are more compressed than the recent Anatinz, but it can 
scarcely be considered generically distinct. A. rostrata, Agass. 
CERCOMYA, Agassiz, 1842. Shell elongated, compressed; beaks 
fissured; posterior slope frequently angulated, Jurassic, Creta- 
ceous. A. gracilis, of Australia, is a recent species. A. striata, 
Agassiz (cvili, 72). Jurassic. 
pLecToMYA, Loriol, 1868. Shell ovately elongated, equivalve, 
beaks subcentral, a strong oblique rib posterior to them ; hinge 
edentulous ; ligament external. Based ona well-known Jurassic 
fossil, the Tellina rugosa of Romer. Appears to be scarcely 
distinguishable, however, from Platymya. 
PERIPLOMYA, Conrad, 1870. (Leptomya, Conrad [not A. 
Adams ], 1867. Fligemayers Stoliczka,1870.) Shell oblong, perla- 
ceous, gaping anteriorly ; hinge with a spoon-shaped cartilage- 
process, forming an oblique callosity, which extends to the ear- 
dinal margin; an obsolete rib and fissure run obliquely from the 
anterior side of the beak. The genus is evidently closely allied 
to Anatina, from which it chiefly differs by the rib and fissure 
anterior to the beak. Based on a North American cretaceous 
species. P. applicata, Conrad. 
ANATIMYA, Conrad, 1860. Shell oblong, like an Anatina, ante- 
rior side with concentric sulci, posterior with radiating ribs. 
Only American and cretaceous. A. anteradiata, Conr. (cviii, 73). 
ANTHRACOMYA, Salter, 1861. 
Etym.—Anthrax, coal, and mya, a generic name. 
Syn.—Naiadites, Dawson. 
Distr.—9 sp. Coal-measures, associated with marine animals. 
Great Britain, Nova Scotia. A. Adamsi, Salter. 
Shell thin, equivalve, the right valve rather larger; valves 
close, oblong, wider behind, where there is a blunt siphonal 
ridge ; rounded anteriorly, with a byssal sinus on the anterior 
ventral edge. Beaks small, anterior, and slightly prominent, 
