76 EOCENE MOLLUSCA. 



Modiola Deshayesiana? /. Sowerby. Tab. XIX, fig. 19. 



A shell from Mr. Edwards's cabinet here represented is referred with doubt to the 

 Bracklesham species. The figure 14 of Tab. XIII was copied from Mr. Dixon's work, 

 and a comparison could not be instituted. I have therefore thought it desirable to 

 represent the present specimen, as it presents a difference in outline, and may possibly 

 belong to another species ; at least it constitutes a variety, which I will call Hemp- 

 steadiensis. 



The form of our fossil is more pointed in the siphonal region than the figure of the 

 Bracklesham or the Paris Basin specimens ; it is less regularly cylindrical, and not so 

 elongated, and there is a considerable slope from the extremity of the hinge-line to the 

 siphonilateral margin. Several casts of specimens have been found, and there is on one 

 individual a portion of the shell remaining which is very smooth and glossy, and with a 

 magnifier the fine and faint cross or radiating striae may be seen. The animal appears 

 to have formed for itself a thickened lining to the crypt in which it dwelt. The only 

 locality at present known is Hempstead, where it is found embedded in the shell of an 

 oyster. 



In the ' Quarterly Journal of the Geol. Soc.' for November, 1862, p. 330, is a paper 

 by Dr. Sandberger, in which he speaks of a fossil from Hempstead as identical with Mod. 

 delicatula, Desh. This British fossil was received by him from Mr. Edwards, and is the 

 same species as the one I have had figured, but I cannot coincide in Dr. Sandberger's 

 opinion. The following differences appear to me to be sufficient to keep the English and 

 the French shells specifically distinct. The umbo is more terminal, the ventral margin 

 less convex, the dorsal or hinge area shorter, and the siphonal region is more oblique and 

 pointed in our shell than in M. delicatula. My comparison is dependent upon the 

 characters given by M. Deshayes ; but judging from the figure and description by that 

 accurate and able naturalist, I think the two forms cannot be specifically united. 



23. Modiola (?) consobrina, 8. Wood. Tab. XIX, fig. 17. 



Length, 2 inches. 



Locality. Alum Bay (Fisher). 



One specimen is all that I have yet seen, and that unfortunately is not in a condition 

 for fair determination. It was found, Mr. Fisher tells me, in the Bracklesham bed at 

 Alum Bay ; the specimen is firmly imbedded in the matrix (a sandy marl), by which the 

 interior is hidden, and the umbonal region is not quite perfect. It differs from M. sub- 

 cancellata principally in having fewer and coarser rays, and it has not the concentric ridges 

 or distinct lines of growth subcancellating the exterior of that species. The figure has 



