372 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



"Wood), allied in appearance to P. tetragona (otherwise Murex alveo- 

 latus). 



The following is a list of the shells, so far as I have been able to 

 decipher them from their broken and water- worn fragments : — 



Cyprina rustica. Not very nncommon. 



G. Islandica. Very common, being the most plentiful shell of the 



deposit. 

 Astarte. Apparently several species; bnt the condition of the 



fragments renders their identification difficult. 

 Venus. Apparently of more than one species ; but, judging from 



the hinge-pieces, V. casina is the most common. 

 Artemis lincta. A few fragments. 

 Cardium. Not uncommon, and of more than one species, some of 



them of large size. 

 Pecten. Several species. The most common, so far as I can 



make out from the remains, seems to have been P. opercularis, 



var. Audouini. One small bit looks like P. maosimus, while 



the ribbing of another is more like that of P. princeps. 

 Pectunculus glycimeris. Common ; and it seems to have attained 



a good size. 

 Tellina solidula. Of some specimens sent to Mr. S. P. Woodward 



two years ago, he wrote me, " There are two specimens of the 

 Tellina of unusual thickness. Mr. M' Andrew would scarcely 



believe it this species (T. solidula) ; but it is like no other." 

 Mya, apparently M. truncata. One or two pieces. 

 Fusus antiquus. Not very uncommon. 

 F. antiquus, var. contrarius. Three or four fragments. 

 Mangelia, like M. turricola, but distinct. One specimen. 

 Purpura lapillus, var. incrassata of S. Wood. One specimen. 



Besides these, I have fragments of other species which I have not 

 yet been able to identify. The whole of those above enumerated are 

 found in the Crag of England ; while the character of the group is 

 different from the usual assemblage met with in the drift-beds of 

 this part of Scotland. For instance, Pecten Islandicus is the only 

 Pecten I have found in the drift ; and none of the fragments from 

 these supposed Crag beds appear to belong to it. We miss also 

 Tellina proxima, Natica, and other common drift-shells. 



The materials of the strata are all very much water- worn, and 

 indicate long roiling about in a shallow sea. The shells have suffered 

 similar treatment, and are accordingly so broken and worn as to 

 render their identification very difficult. I have gathered hundreds 

 of fragments, but have never yet got one perfect specimen. Some of 

 the pieces are filled with a hard stony crust ; and occasionally indu- 

 rated, calcareous nodules are met with full of comminuted shells. 

 Owing to the covering of drift, however, the beds are very badly 

 exposed ; but the mass in many places reaches a thickness of 30 or 

 40 feet, and in some cases a good deal more. 



If I am right in referring this sand and gravel to the age of 

 the Crag, it will throw some light upon the origin of our chalk-flints ; 



