240 MOLLUSCA FROM THE CRAG. 



4. Abra obovalis, S. Wood. Tab. XXII, fig. II. 



Amphidesma obovale. S. Wood. Catalogue, 1840. 



Erycina ovata ? FAil. En. Moll. Sic, vol. i, p. 13, t. 1, fig. 13, 1836. 



Tellina rubigisosa? Poli. Vol. i, p. IS, t. 1,"), fig. 31, 1791, sec. PAH. 



Spec. Char. Testa ovata, crassiusculd, subaquilaterali ; antice rotundatu, convex a ; 

 po.stice anyidatd, compressiusculd ; dentihus lateralibus magnis, elevatis, approximatis ; 

 apicibiis promimdis ; impressione palliari magno prof undo. 



Sh(!ll ovate, rather thick, nearly equilateral, smooth ; anterior side rounded, some- 

 what tumid ; posterior angulatcd, and slightly compressed ; lateral hinge teeth large, 

 elevated, and proximate ; apices rather prominent ; palleal impression large and deep. 



Length, \ inch nearly. Height, f inch. 



Localiti/. Red Crag, Sutton. 



Mam. Crag, near Norwich. 



Only two spccimeus of this species have come under my observation ; one was from 

 the Mam. Crag, given to me by Mr. Charlesworth, the other I found in the Red Crag at 

 Sutton : they are both unfortunately the right valve. Perhaps the shell described by 

 Philippi above referred to is the same species, but the figure is by no means good, and 

 the description does not altogether accord with the Crag shell, which is thick, and not 

 thin, as therein described ; our shell has a remarkably thick hinge and a large, angular, 

 or spoon-shaped area for the cartilage, behind which arc two small cardinal teeth, and 

 at a little distance are two prominent angular denticles ; the posterior one close to the 

 extremity of the hinge pit ; the palleal sinus is very large, extending into the shell more 

 than two thirds of its entire length. It differs from A. tenuis in being more pointed, 

 and it has a more strongly marked hinge. 



A shell much resembling this species has been obtained on the N. E. Coast of 

 America, called Cummivgia trUinoidcs, Conrad, 1830, Gould, ' Invert. Massach.,' p. 56, 

 fig. 3G, and Stimpson ' Catal.,' p. 20, but it is specifically distinct. The Crag shell is 

 not so much compressed ; the ventral margin is more convex, and the lateral teeth of 

 the hinge larger and more prominent; while the American shell is also different 

 externally, being covered with larger and more regular ridges. 



Erycina ovata. Midden, t. 19, figs. 5 — 8, as well as Amphidesma ovata, Desh. ' Exped. 

 Moree,' pi. 6, fig. 8, ai)pear, from the figures and descriptions, to be different froni our 

 shell. 



Mactra,* LinncB^us, 17G7. 



Callista Callistoderma (sp.) Poli, 1791. 

 Trigoxella (sp.) Ba Costa, 1778. 

 MuLlsiA. Gray, 1836. 



Spiscla. Gray, 1837; 18.51. 

 Mesodesma (sp.) Desh. 1835. 

 Hemimactra. Swains. 1840. 



Etym. fiuKrpa, a kueading trough. 



