VENUS. DIMYARIA. 99 
species the central tooth is deeply so; two lateral, some- 
what rounded muscular impressions in each valve ; mantle 
muscular impression with a large sinus; ligament external, 
and partly concealed by the dorsal margins of the valves. 
Pullastra recondita. Plate IX. fig. 26. P. globosa. 
Plate X. figs. 3 and 6. 
This genus was established by Sowerby for the reception of Lamarck’s 
Venus Pullastra, Virginea decussata, and their congenerous species, to which 
he has most properly united the whole of the species forming Lamarck’s genus 
Venerupis, whose characters entirely agree with the above named Veneres ; 
and the animals are also of the same natural genus. 
The Pullastre are marine shells. They occur in a fossil state, and are 
only found in the Tertiary formation. 
Genus XXV.— VENUS. — Linneus. 
Generic Character.— Shell smooth, equivalve, inequila- 
teral, transverse, subglobose or suboval ; external surface 
sometimes rugose, margin close; three divergent cardinal 
teeth in each valve, all approximate ; umbones prominent 
for the most part, with a cordiferm depression immediately 
below them; two lateral, remote, somewhat orbicular mus- 
cular impressions, united by a pallial impression, which is 
generally sinuated behind; ligament external, although 
sometimes almost hidden by the extension of the outer 
edge of the shell. 
Venus incrassata, Plate VIII. fig. 4. 
This extensive genus requires to be separated into the following sections. 
SUB-DIVISION I. —Lunule distinctly circumscribed by an impressed line. 
Section 1. Somewhat cordiform, generally a little acuminated and rounded 
anteriorly, sinus of the pallial impression nearly obsolete; each valve with 
two large distinct divergent teeth, and a small tooth which is anterior in the 
right valve, and posterior in the left; asin V. Paphia. 
Section 2. Subovate, anterior side considerably shorter than the posterior ; 
generally lamellose or longitudinally grooved externally ; each valve with three 
strong divergent cardinal teeth, the two anterior ones emarginate in one valve, 
and the two posterior ones in the other, with a moderately sized siphonal 
impression, and a little rounded. V. purpurata, illustrates this section. 
Section 3. Like those of section 2, but with external, thin, remote lamelle ; 
pallial impression anteriorly acuminated, and very small; central cardinal 
teeth large and thick; the others small and thin; the anterior somewhat 
curved, as exemplified in V. dameliosa. 
ection 4. Exteriorly rough and cancellated ; the central and posterior teeth 
in the right valve large, thick, and emarginate, the anterior linear and thin ; 
in the left valve the central tooth is thick and emarginate, while the anterior 
is elongated, thick and linear; posterior tooth small, linear, thin and nearly 
obsolete ; pallial sinus rounded in front, and of moderate size. 
