232 ORGANIC REMAINS. 



incurved remote beaks, with a broad flat space intervening ; -which 

 space or area is elegantly marked with four sets of straight lines, 

 parallel to the edges of the area, meeting in the hinge line at one end, 

 and in a line passing from beak to beak at the other. The shell is 

 marked with transverse lines ; but the markings in our specimens are 

 somewhat defaced. 



In some of our ironstone beds, we find a shell greatly resembling 

 the area glycymeris ; but we have not discovered the hinge. 



Pecten. Scallop. Few shells are more abundant in our strata 

 than this ; the oolite, the ironstone, and the calcareous sandstone 

 being replenished with a great variety of species. These species it is 

 not very easy to distinguish and describe ; as they generally occur in 

 single valves, with the ears more or less mutilated. Some of our 

 most beautiful and singular scallops are delineated in Plate IX. 



Fig. 8 represents the inside of a valve, belonging to a species 

 that is either the pecten suhrufus ( or opercularis ), or one nearly allied 

 to it. It is from the Staiths beds, and measures two inches each 

 way. Very large specimens, of the same form, measuring four or 

 five inches, occur in the sandstone and ironstone bands in the alumi- 

 nous strata. They have been supposed to belong to p. maximus or 

 jj. jacohaeus; but they differ considerably from both these species, 

 having both valves convex, though not equally so. Of these shells 

 we may distinguish two species ; one with decussated striae, or striae 

 both longitudinal and transverse, which we may consider as the p. 

 suhrufus ; and another having remarkably rounded ribs with flat inter- 

 vals, marked only with fine transverse striae. The latter species 

 agrees with the p. equivalvis of Sowerby, Tab. 136 ; only the ribs in 

 our shells, instead of being narrower than the intermediate spaces, 

 are usually much broader. The number of ribs, both in this species 

 and in the p. suhrufus, varies from eighteen to twenty-two, twenty 

 being the average. 



