BIVALVIA. 77 



been a little too much improved at the umbo, and it is difficult in its present condition 

 to say whether it belongs to Mytilus or Modiola. Its present name is merely 

 provisional. 



16*. Modiola subcarinata ? Lamarck. Tab. XIX, fig. 20. 



At page 71, Tab. XII, fig. 9, is figured and described a shell from the London Clay 

 at Highgate, and referred with doubt to Lamarck's species from the Paris Basin. 

 Mr. Edwards has since obtained a specimen from Barton, with the general characters 

 of the French species, although differing in some minor particulars, and I have thought it 

 desirable that it should be represented. In comparing our present specimen with the 

 figure of the Paris Basin species, there appears a difference in the length of the hinge-area, 

 and also in the direction of the margins, both the dorsal and ventral margins being more 

 curved in the French shell than in our own ; there is also a slight difference between 

 the Barton specimen and the one previously figured from Highgate, which has a more 

 prominent or subcarinal projection, with the umbo rather more terminal. 



Our shell is covered with elevated or rather imbricated lines of growth, and these are 

 more distant upon the siphonal region than upon the other parts of the shell ; they appear 

 as if they once supported a fringed epidermis like that which ornaments the shell which 

 has been called M. barbata. 



Since the above was written and the figures engraved, I have seen a specimen in the 

 cabinet of Mr. Prestwich of the following dimensions : — 3| inches in length, with a height 

 or breadth of 1 in., and a tumidity of an inch and half: this was obtained at Clarendon 

 Hill, near Salisbury, and I presume it to be the same as M. subcarinata from Highgate. 



24. Modiola subcancellata, Edwards, MS. Tab. XIX, fig. 15. 



Locality. Barton {Edwards). 



An imperfect specimen has recently come into the possession of Mr. Edwards, to 

 which is attached the above specific name. It bears considerable resemblance to two 

 species from the Paris Basin, viz., Mod. Rigaultii, Desh. ('An. sans vert, du Bass, de Paris, 

 t. 1, p. 29, pi. 74, figs. 23, 24), and Mod. Levesquei (id., p. 30, pi. 75, figs. 4, 5) ; our 

 shell appears to approach rather nearer to the latter, and, if the specimens themselves 

 could be compared, might possibly be referred to that species ; there are, however, some 

 differences which may be here pointed out. The Barton shell does not appear to have 

 been so broad or so high as that of the French species, neither has it so long an area for 

 connexus ; the dorsal edge is finely but deeply denticulated, as that of M. Levesquei is 

 also represented to be, but it does not appear so much curved as in the latter. There 



