BIVALVIA. 221 
more or less uncoated. Unlike the preceding species, this is free from radiating striz, 
and the margin is in consequence quite smooth. The form of this is also different, 
and may be readily distinguished. The palleal sinus is large and deep, extending 
beyond the hinge area, and in some old shells the interior is considerably thickened. 
Poli has given a good representation of the shell of this species; but in depicting 
the animal he has made the siphons to protrude on the longer, and the foot at the 
shorter or posterior side. 
PsamMosta,* Zam. 1818. 
Lux. Chemn. 1782. ] PERONEZA et PERONHODERMA (sp.) Poli. 
Gari. Schum. 1817. | Azor. Leach, MS., 1819. } sec Gas 
Psammorza. Lamk. 1818. Gosreus. Id. ‘ Z- 
PsamMoTEa. Schweig. | PsamMocoLa. Blainv. 1824. 
Generic Character. Shell equivalve, subequilateral, transversely oblong, more or 
less compressed, slightly gaping at each extremity; exterior generally covered with 
transverse or concentric striz, and occasionally ornamented with radiating lines or 
ridges. Hinge composed of two teeth in one valve, and one in the other, and without 
lateral teeth. Sinus in the impression of the mantle large and deep. Ligament 
external, fulcrum prominent. 
The animal has the mantle open the entire length, and bordered by a fringe of 
fine simple filaments ; siphons long and slender, marked with longitudinal lines, and 
ornamented with minute cirri; a large and tongue-shaped foot, somewhat pointed. 
There is no very essential distinction between this genus and Te/lina, the 
greatest difference appearing to be a somewhat more oblong form of outline, and 
a less distinct inflexion on the posterior side of the shell, with a rather more 
prominent fulcrum for the ligament in Psammobia. In the recent state the 
species are, like the Tellens, inhabitants of various climes, and generally live buried in 
sand or gravelly mud, and they have a vertical range from low-water mark to 100 
fathoms. 
The name of this genus, being in fact only third in point of date, will have to be 
changed. 
1. PSAMMOBIA FERROENSIS, Chemn. Tab. XXII. fig. 3, a, 0. 
Petiver. Gazophyl., t. 94, fig. 9, 1764. 
TELLINA FERRGENSIS. Chemn. Conch. Cab., vi, p. 99, t. 10, fig. 91, 1782. 
—  Ferdensts. Broce. Conch. Subap., p. 512, No. 6, 1814. 
* Etym. Wappos, sand, and Bidw, to live. 
