162 GASTROCH ANID A. 
valve is usually more convex than the left, which m most 
specimens locks into it, like that of the Pandora obtusa and 
Corbula nucleus. This species, though less smooth and regular 
than our Sphenia Binghami, is nevertheless extremely similar 
both as to shell and animal, and has, in consequence, been 
often confounded with it; it is, however, distinct, and the 
dentition always preserves a constant different character. 
VENERIRUPIS, Lamarck. 
V. rus, Linneus. 
V. irus, Brit. Moll. i. p. 156, pl. 7. f. 1, 2, 3; (animal) pl. G. f. 2. 
Donaz irus, Auctorun. 
Conchologists, by the character of the teeth of the only 
species of this genus, would place it amongst the Veneride, 
but malacology informs us, that it is as decided a member of 
the Gastrochenide as Saxicava. We have examined a fresh, 
though not a live animal, taken alive on the southern coasts ; 
the closed mantle, foot, and siphons are similar to the Saw- 
cave. Dead shells are often procured in the red sandstone at 
Exmouth, but it has not occurred there in a living state; it is 
only found in deposits that have been partially deserted by the 
sea; we have little doubt, that if the rocks which are never 
uncovered at the lowest tides could be examined, it would 
be found alive. We have here a practical illustration of the 
superior attributes of malacological determinations. 
PANOPAMA, Menard de la Groye. 
P. norvecica, Spengler. 
P. norvegica, Brit. Moll. i. p- 174, pl. 11, and iv. p. 249. 
Mya norvegica, Auctorum. 
Animal oblong, thick, pretty much the shape of the shell, 
which gapes basally at the anterior end, and is obliquely 
truncate posteriorly, with a very large gape. Mantle thick, 
closed, except the pedal and siphonal apertures, pale drab, 
but covered with a black skin. The orifice for the issue of 
