CLASS PELECYPODA 
199 
Mya intermedia Dali, 1898. 
Plate 15, fig. 5. 
Trans. Wagner Inst. Sci., 3; pt. 4:875. 
This species is intermediate in character between M. arenaria and M. 
truncata, there are constant though not conspicuous differences in the 
hinge. This species grows to a very large size on the Alaskan Peninsula 
and is very puzzling. Length about 6 inches. (Dali.) 
Type in U. S. N. M. Type locality, Alaska. 
Range. From Point Barrow in the Arctic Ocean to Monterey, Cali¬ 
fornia. 
Genus Cryptomya Conrad, 1837. 
Shell inequilateral, transverse, oblong, gaping behind; valves with 
radiating (sometimes crossed by concentric) striae; right valve with a 
lamellar tooth, left valve with a broad fossette; ligament internal; pallial 
impression with a small sinus. (Tryon. S. S. Conch.) 
Type. Sphccnia californica Conrad. 
Distribution. California, Australia, Philippines. 
Range in time. Miocene to Pleistocene. 
Cryptomya californica Conrad, 1837. 
Jour. Acad. Nat. Sci. Phila., 7:234; pi. 19, fig. 11. 
Shell triangular, convex, thick, with numerous, irregular, lamellar, 
concentric striae; posterior side compressed, cuneiform; beaks central, 
rather prominent; lateral teeth prominent. Length, 1J4 inch. (Conrad.) 
Type locality, near Santa Barbara, California. 
Range. Chichagof Island, Alaska, to Topolobampo, Mexico. 
Genus SPHENIA Turton, 1822. 
Shell oblong, inequivalve, inequilateral, more or less gaping anteriorly. 
Surface of the valve smooth or rugose, covered with an epidermis. Beaks 
incurved. Hinge composed of an erect, dilated laminar tooth in one valve, 
with a corresponding pit in the other. Ligament internal. Pallial impres¬ 
sion with a slight sinuation. This rare and curious genus is as yet but very 
imperfectly known. The shell has evidently, at a glance, a striking resem¬ 
blance to Saxicava. (British Mollusca). Forbes and Hanley. 
Type. Sphenia binghami Turton. 
Distribution. Britain, West Coast of North America, Red Sea. Bur¬ 
rowing in limestone, oyster-shells and in roots of kelp, from deep water. 
Range in time. Tertiary. 
