﻿112 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 8, 



other rather compressed and wider posteally. The latter is the Cy- 

 clas media of Sir Roderick Murchison's list. After a careful compa- 

 rison of this Cyrena with Mr. Robertson's Brora specimens, and the 

 large series from the Purbeck, Hastings sands, and Wealden, in the 

 Museum of Practical Geology, I feel bound to consider it distinct. It 

 is a characteristic shell of the Staffin beds, and is found in large 

 masses. I have dedicated it to Professor Jameson, a memorial of 

 his many and valuable researches in the Hebrides, and as a token of 

 respect from one, who esteems as a high honour the good fortune of 

 having been a pupil of that eminent geologist. 



Cyrena a rata. Plate V. fig. 6 a, 6 b. 



Shell much depressed, very inequilateral, posteally abbreviated, 

 ovate-subquadrate, surface regularly sulcated concentrically, ridges 

 acute, numerous, narrower than the interspaces. Breadth T \ths, 

 length y ¥ ths of an inch. This very distinct species is comparatively 

 scarce, and not gregarious. 



Cyrena Cunninghamii. Plate V. fig. 9 a, 9 b. 



Shell depressed, subinequilateral, subquadrate, wide and subtrun- 

 cated anteally, rounded posteally, anteal extremity just above the 

 frontal margin ; surface obsoletely wrinkled by layers of growth ; beaks 

 not prominent, rather obtuse. 



Length of a large specimen of an inch, breadth 1 inch ; 



thickness half an inch. 



This appears to be distinct from C. Jamesonii, and is easily recog- 

 nised by its small and depressed beaks. I have dedicated it to the 

 memory of my late friend and fellow-student, Mr. Hay Cunningham, 

 whose Memoirs on the Geology of Scotland held out hopes of future 

 discoveries, too soon destroyed by his premature death. 



Cyrena MacCullochii. Plate V. fig. 10 a, 10 5. 



Shell tumid, strong, more or less subtriangular, abbreviated post- 

 eally, obliquely subangulated anteally, surface with frequent and close 

 lines of growth, beaks very prominent. Length T 9 ¥ ths, breadth yfths, 

 thickness yVths of an inch. This Cyrena is constantly associated 

 with the Pema. It varies considerably in characters and outline, but 

 appears to be distinct from its congeners, and to occupy a special 

 horizon in this series of estuary beds. I have named it in honour of 

 the eminent investigator of the geology of Scotland, who called atten- 

 tion to the series of oolitic beds in Skye. 



Potamomya ? Sowerbii. Plate V. fig. 2 a, 2 b. 



Shell transversely ovate, subequilateral, inequivalve (?), rather tu- 

 mid, somewhat expanded anteally, frontal margin rounded, surface 

 striated by lines of growth, beaks prominent. Breadth 1 inch and 

 T 3 T ths, length T \ths of an inch, thickness half an inch. 



This is the tf bivalve referable to TJnio or Anodcn" of Sir Roderick 



