GASTEROPODA. 187 



linearly arranged, and on the lateral areas the strise are transverse or diverging ; 

 apophyses subangular, projecting, and sublateral. 



Altitude of ' arch , \ the span. 



Locality. Cor. Crag, Sutton. ? Mediterranean. 



Single valves of this species are abundant. It was considered in my Catalogue 

 as a distant species ; I have now united it with the above Mediterranean species, 

 from its general resemblance, although with considerable doubt. The lateral areas 

 have the granules in transverse or radiating striae, not quite so regular and distinct 

 as those upon the dorsal area ; but the primal as well as the final valves have the 

 different areas striated in a radiating manner. The projecting processes are near 

 the sides, and are of an obtusely-angular form, somewhat resembling the blade of a 

 lancet used for bleeding cattle. On the final valve they do not project so much, 

 and extend further along the margin inwards. Fig. 11 a is the primal valve ; 11 b, 

 one of the central valves ; 11 c, the terminal or final valve. 



There is every reason to believe that two more species of the genus Chiton 

 existed during the Coralline Crag period, valves of which are in my cabinet. They 

 are not, however, in sufficiently good preservation for description, and their 

 characters cannot be accurately determined. 



Oed. CIBRIBBANCHIATA. 



Dentalium.* Linn. 1740. 



Tubulus Scilla. (ex Hermanseri). 

 Solen (spec.) Rumph. Id. 



Gen. Char. Shell tubular, symmetrical, elongato-conical, or subcylindrical, 

 generally smooth, sometimes annulated, often costated, slightly curved, open at 

 both ends, smaller at the posterior extremity, which is sometimes entire, sometimes 

 with a medial and dorsal cleft, occasionally with two lateral indentations. 



Animals of this genus are now determined to be true Mollusca, though belong- 

 ing to a distinct order, having the branchiae near the upper part of the neck, in the 

 form of two bundles of fine, soft, flexible, tentacular filaments. They are placed 

 in a natural arrangement near the Patellae. M. Deshayes, in a Memoir read before 

 the Societe d'Hist. Naturelle, 1825, gave the anatomical details of one species, and 

 a monograph of the genus. In his description he places the shell with its small 

 end downwards, considering it the posterior extremity ; and the convex portion of 

 the shell, as corresponding with the dorsal surface of the animal; the larger end, 

 therefore, is the anterior. 



* Etym. Dentate, from dens, a tooth. 



