﻿BIYALVIA. 



141 



Crenulated in the mature state. 

 Astarte Basterotii. 

 Burtinii. 

 crebricostata. 

 crebrilirata. 

 incrassata. 

 Galeottii. 

 mutabilis. 

 obliquata. 

 pygmaea. 

 Omalii. 

 sulcata, 

 triangularis. 



Sot crenulated at any stage of growth. 



Astarte borealis. 

 ,, compressa. 

 elliptica. 

 Forbesii. 

 parvula. 



The different formations to which these species belong will be found in my Com- 

 pendium or General Table. 



Woodia digitaria. Crag Moll., vol. ii, p. 190, Tab. XVII, fig. 8 {asjstarte digitarid) ; 



Supplement, Tab. X, fig. 8 a. 



Localities. Coralline Crag passim. Red Crag, Walton, Bentley, and Butley {Bell). 

 Middle Glacial, Hopton. 



Var. Hojotonensis, Supplement, Tab. X, fig. 8 5. 

 Locality. Middle Glacial, Hopton. 



The small shell represented in ' Supplement,' Tab. X, fig. 8 b, is from the Middle 

 Glacial sand of Hopton, and as it seems to differ materially from the Coralline and Red 

 Crag specimens I think it deserving of a separate figure. This Middle Glacial shell is 

 much less transverse than any of my specimens from either the Coralline 1 or Red Crags, 

 and the elliptical markings much more distant, being scarcely half so numerous as in the 

 Cor. Crag specimens. I have found specimens of the same species at Walton Naze and 

 they are of an intermediate form, with the elliptical lines more distant than those upon 

 the Cor. Crag specimens, but not so much so as upon the Glacial one, while the form 

 of all the Red Crag specimens is generally even more transverse than the Coralline 

 Crag ones. 



I had another figure (' Supplement,' Tab. X, fig. 8 a) made of the Cor. Crag shell 

 in order to show the ornamentation on the posterior side of the shell, which is not 

 distinctly shown in the figures in Tab. XVII, but the artist has not been fortunate in his 

 representation. These are transverse to the sulcations and form ridges upon them. They 



1 Since the above was in type I have found in the Coralline Crag a specimen presenting the elliptical 

 markings nearly as distinct as in the Hopton specimen. This, however, is the only example presenting that 

 feature which I have met with among the very numerous Coralline Crag specimens of this species that have 

 passed through my hands. 



