BIVALVIA. 185 
procured in the Arctic seas. In a comparison with the recent shell, some slight 
difference may be observed, the Crag one being somewhat compressed, with a rather 
more elevated umbo; in the two specimens belonging to Mr. Morris, there is a dif- 
ference, one being less transverse than the other, and the smaller of the two has the 
margin of the valves deeply crenulated, while in the other it is quite smooth, and in 
both the umbo is much eroded, thereby considerably reducing its elevation, but in the 
Crag shell the umbo has not in the least been acted upon in that manner. There is a 
considerable resemblance with 4. gracilis which is also found in the Red Crag, but 
that species is more equilateral, with the sculpture more distinct and elaborate. 
12. ASTARTE GRACILIS, Minster. Tab. XVII, fig. 3 a—e. 
ASTARTE GRACILIS. Miinst. apud Goldf. Pet. Germ., vol. ii, p. 194, t. 135, fig. 4a—e. 
—  PROPINQUA. Id. PP vol. li, p. 194, t. 135, fig. 3 a—e. 
— Gatzzorri. Nyst. Coq. Foss. de Belg., p. 159, pl. vi, fig. 17 a—e. 
— 1rata. Conrad. Sec. Lyell Proc. Geol. Soc., 1845, p- 555. 
Spec. Char. Testa orbiculato-trigonuld, ovatd, transversd, tumidd aut compressiuscula 
plurimim subequilaterali; lineatd vel suleatd, lineis magnis convevis ; margine crenulato 
vel integro. 
Shell roundedly trigonal, ovate, transverse, tumid, or compressed, for the most 
part nearly equilateral, ridged or sulcated externally, with large rounded lines ; margin 
crenulated or smooth. 
Diameter, ths of an inch. 
Localities. Cor. Crag, Sutton, Ramsholt, Sudbourn, and Gedgrave. 
Red Crag, Sutton, Bawdsey. 
This species is very abundant in the Coralline, while a few Specimens only, and 
those not in very good condition, have been found by myself in the Red Crag. The 
most common variety is that which corresponds with the figure by Goldfuss; this is 
very regular in shape, nearly equilateral, longer than high, and covered upon the ex- 
terior with about forty or fifty rounded, regularly-formed ridges, wider than the spaces 
between them upon the body or older part of the shell, while in the younger or in the 
umbonal region these ridges are somewhat sharp upon the hinder or upper side, or, as 
it were, obtusely reflected ; the same character in regard to the ridges pervades all the 
varieties, and covers the entire surface, except the lunule and corselet, which are 
smooth; another form is more trigonal, has a thicker hinge, with a more prominent 
umbo, and is quite as high as it is long; var. multilineata, (fig. 3 e,) of which I have only 
a few specimens, varies in no other character than a greater number of these con- 
centric ridges, amounting in these to as many as 90; the shell is very thick, tumid, 
and elevated, and is as high as it is long. In the full grown state the shell is crenulated 
at the margin, and although large specimens are often met with in which this part is 
quite smooth, these have not, it is presumed, attained to full maturity. It was probably 
