BIVALVE SHELLS. 227 



dimensions are, — about an inch long, an inch and a quarter broad, 

 and three quarters of an inch thick.* 



The shell figured by Parkinson, III. PI. XIII. Fig. 3, and named 

 by Sowerby (Tab. 14) c. hillanum, is not the same with our cockle. 

 The principal striae in the front of our shell are elegantly bent, 

 meeting in the line of the hinge ; and these curved striae are crossed, 

 in the parts furthest from the beaks, by a few straight striae, rather 

 faint, diverging from the hinge line. The curved striae not only 

 cover the area, but encroach a little on the disks, on each side. The 

 beaks are incurved, so as nearly to meet. 



Small shells resembling the c. ciliatum, are not uncommon in the 

 lias seams and nodules, in the oolite, and the calcareous sandstone. 

 Fig. 16, PI. VIII, represents a specimen from the oolite, which in the 

 number and minuteness of its ribs, or longitudinal striae, resembles 

 c. serratum. Nodules containing large collections of shells of this 

 kind, some of them very minute, are frequently met with in the alum 

 shale near Whitby. Not having seen the hinge, we have doubts 

 whether these shells belong to this genus. Fig. 1 is another small 

 shell, from the ironstone, resembling Fig. 16 in the number and 

 minuteness of its striae ; but it is more ventricose, and has a more 

 depressed area. 



Tellina. Of this shell a few species only can be particularized. 

 Fig 2, PI. VIII, corresponds with the t. crassa. It is from the 

 Malton oolite. It differs little from the t. ohtusa of Sowerby, 

 Tab. 179, Fig. 4. A shell like t. fragilis occurs in the ironstone 

 beds, and others that may be ranked under this genus are found in 

 the oolite. 



* It may be necessary to apprise some readers, that the length of a shell is the distance 

 from the beaks, or the region of the hinge, to the opposite margin ; and the breadth is a line 

 at right angles to that direction. In some shells, particularly those of the solen family, the 

 breadth is vastly greater than the length. 



