11 
rhomboidal; smooth; pointed in front; and scarcely winged. 
Tunstall. 
Bysso-arcci tumida, J. de. C. Sow. Common. 
Bysso-arcci Kingiana, de Verneuil. Rarer than the last. 
Leda Vintii, n. sp. Form a little inequilateral: anterior 
end the shortest, and rounded: posterior end attenuated, and 
rounded at the extremity: umbones rather tumid, and turned 
posteriorly: surface marked with slightly-waved prominent 
transverse lines, which suddenly become nearly obselet.e on 
the posterior third of the valves: pallial sinus very small. 
Humbleton, Byers’ quarry, and Whitley. 
PLEUROPHORUS, n. gen. Form inequilateral: cartilage ex¬ 
ternal: anterior adductor muscular impressions deeply exca¬ 
vated, often bounded posteriorly by a ridge : pallial line 
entire : dentition cardinal and posterior : cardinal teeth two 
in each valve, diverging inwardly, and interlocking alternate¬ 
ly : posterior teeth linear; the receiving tooth in the left valve. 
Pleurophorus costatus, Capt. T. Brown. Rather common. 
Schizodus truncatus, n. sp. Axinus id., King; and A . 
parallelus, King, cited in “ Geol. Russ.,” vol. 1, p. 224. This 
species is less obliquely truncated at the posterior end than 
Schizodus (Axinus) obscurus: it is finely concentrically 
threaded, more decidedly on the anterior than on the posterior 
half of the valves: its coloration consists of small spots on 
a light dark ground, resembling that of the recent Circe 
Castrensis. Rather common. 
Solemya Phillipsiana, n. sp. This species has^he anterior 
border of the posterior adductor muscular impressions corres¬ 
ponding to a line drawn vertically from the umbone to the 
ventral margin; and is marked externally with flat slightly- 
raised spreading bands rather distant from each other. 
Humbleton. 
Solemya biarmica ? de Verneuil. Tunstall Hill and Hum¬ 
bleton. 
Astarte Vallisneriana, n. sp. Slightly inequilateral: ven¬ 
tral outline semicircular: umbones pointed: dorsal slope ot 
each valve angulated: concentrically threaded. Whitley. 
