64 MOLLUSCA FROM THE CRAG. 



both extremities, middle space smooth, posterior side of the shell broader than the 

 anterior. 



Longest Diameter, \ an inch. 



Locality. Mam. Crag, Chillesford. Recent, Britain and Seas of Norway. 



A specimen strongly resembling this species is in my Cabinet, obtained in the 

 native bed of the Mammaliferous or Newer Crag Period, at Chillesford. The shells 

 in that deposit are excessively fragile, and are preserved with difficulty. This 

 specimen appears also to have lost a portion of its outer surface : there is, however, 

 upon the exterior, traces of what the sculpture has been, and as far as it can be observed, 

 it seems to correspond with that upon the recent shell, it is, therefore, appropriated to 

 the above species without much doubt ; and, as its congeners in the same deposit are 

 such as we know to be its associates at the present day, it might fairly be expected 

 in that Formation. In the recent state it is considered more of a Boreal form, with 

 but a limited range to the Southward. The earliest appearance of this species is 

 in the upper portion of the Crag, where it seems to have been by no means 

 abundant. I have found it in the recent state upon the shore of the Coast of Suffolk, 

 in pools of water, left by the retreat of the tide. 



8. MODIOLA RHOMBEA, Berkeley. Tab. VIII, fig. 8. 



MODIOLA PRIDEAUXIANA. Leach. Zool. Miscel., vol. ii, p. 35, 1815. 



Brown. Brit. Conch. Illust., pi. 29, fig. 9, 1827. 



RHOMBEA. Berkeley. Zool. Journ., vol. iii, p. 229, Suppl. pi. 18, fig. 1, 1827. 

 Thorpe. Brit. Mar. Couch., p. 107, 1844. 

 Brown. Brit. Conch. Illust., 2d ed., p. 78, pi. 39, fig. 17. 

 ASPERULA. S. Wood. Catalogue, 1840. 



CRENELLA RHOMBEA. Forb. and Hani. Hist. Brit. Shells., vol. ii, p. 208, pi. 45, fig. 3, 



1849. 



Spec. Char. Testa minutd ovato-oUongd vel trapeziformi, tumidd, inflatd, crassd ; 

 costulato-striatd, sulcis vel striis divaricatis ; antice abbreviatd, rotundatd, postice majiore, 

 angnlatd ; margine ventrali sinuato ; natibm prominulis incurvis. 



Shell small ovato-oblong or trapeziform, tumid, or inflated, covered all over with 

 large or costulated bifurcating striae ; anterior side, short and rounded, posterior 

 larger, and angulated ; ventral margin sinuated, with incurved and slightly projecting 

 umbones'. 



Greatest Diameter, \\h of an inch. 



Locality. Cor. Crag, Sutton. Recent, British Seas, and Coast of Sutherland. 



This is considered by the authors of the ' Hist, of Brit. Mollusca,' as an extremely 

 rare shell in the recent state, and somewhat of a modern addition to the Marine 

 Fauna, of the British Isles. Although noticed by Dr. Leach as early as the year 

 1815, it has since rarely been met with and seldom seen in the Cabinets of collectors. 

 It is not so in the fossil, but is very abundant in the rich depot of small shells at Sutton. 



