FROM THE TERTIARY OF VIRGINIA. 235 
I believe, the first species of the genus as yet discovered in a fossil state in this country. 
Hye 1 x * iY f y rs hd 
Mr. Conrad mentions having found the Iistulana elongata, Lam. at Claiborne, but, upon 
comparison with M. Deshayes’ figure of that shell, I do not think that it can be identical 
with the present species. It is larger, more twisted, and has a different sculpture on the 
anterior part. 
The genus Gastrochena, as formed by Lamarck, was placed among the Pholadide, 
and considered to have no tube. M. Deshayes, however, includes it in the venus Fis- 
ae ‘ : 5 x 
tulana, as it inhabits a tube and has no teeth. Mr. Sowerby, again, considers as Gas- 
trochene those species which have a bent tube and an oval shell. According to this 
arrangement, the present species would, most probably, come under this genus, and as 
such I have placed it. 
There are two Gastrochene among the fossils of Great Britain, one from the Oolite, 
the other from the London Clay. Deshayes describes five from the Paris Basin. 
FAMILY PHOLADIDA. 
GENUS PHOLAS. 
P. rHomBorpea, Pr. 34. Fic. 7. 
P. test transversd, oblique rhomboided, valde inequilaterali, posticd rotundato-angulatd, antice rostratd, inflata, tenui, 
medio divisd lined impressd; ared posticd striis levibus concentricis; ared anticd striis acutis Jflexuosis concentricis; margine 
basalt curto; margine dorsali recto, valdé reflexo; palmuld parva, reeurva, tenui; lineis internis duabus elevatis lonvitudi- 
nalibus. 
Shell transverse, obliquely rhomboidal, very inequilateral, rounded-angular posteriorly, rostrate anteriorly, inflated, 
thin, divided in the middle by an impressed line; posterior area with smooth concentric striw; anterior area with 
acute, flexuose, concentric strie; basal margin short; dorsal margin straight, very much reflected; palmule small, 
recurved, thin; two longitudinal internal, elevated lines. 
Diam. .20 of an inch. Length .28. Breadth .18. 
Remarks.—The strie on the anterior part of the shell are sometimes wrinkled so 
regularly that they give it the appearance of being cancellate, although there are no 
radiating lines. ‘The posterior part of the shell is nearly smooth, from the dividing line 
to the umbonial slope, where there are numerous regular lines of growth. ‘There is a 
kind of second dentiform process, immediately below the beaks, formed by the recurving 
of the upper termination of the posterior margin. 'The two internal stri# extend from 
the beaks to the base. The posterior one is situated immediately under the umbonial 
slope. ‘The anterior one is caused by the impressed dividing line. It extends, in a 
point, a little beyond the basal margin. 
This shell is very similar to a specimen of the P. ovalis, Say, without the tube, and 
with the thin anterior basal portion removed, but I believe it to be a perfect shell, as I 
obtained it myself from the hole which it had formed, and in which it appeared to have 
remained undisturbed. It was surrounded by a little indurated mud which preserved 
it entire. It seemed to be entirely destitute of a tube, which character separates it from 
the P. ovalis. It also differs in the shape and size of the palmule, and in the two in- 
ternal lines, 
