Prof. E. Forbes on some Additions to the British Fauna. 411 



of the notch to the apex. The inner margin is undulated and 

 toothed, the deeper impressions marking the compound ribs, the 

 smaller those which are simple. The colour is white. The di- 

 mensions of the largest specimen are — 



Length 1 fe inch. 



Breadth j£. 



Height T 7 2 . 



Apex to anterior margin . . Q\%. 



Length of notch O-^. 



The animal is white, and resembles that of the other Emargi- 

 nula. Mr. MacAndrew dredged this species in Loch Fine near 

 East Loch Tarbet in 25 fathoms, also a single dead specimen off 

 Skipnish near the entrance to Loch Fine. It would appear that 

 Mr. Jeffreys had previously taken it in Loch Carron, and Mr. 

 Alder procured it this year also on the west coast of Scotland. ^^ 



As a fossil it has long been known. It occurs earliest in the 

 coralline crag. The specimens from that deposit which I have J 

 seen are more conical and have fewer fasciculations in the ribs. 

 In the red crag it also occurs, exactly resembling the recent ex- 

 amples. Mr. Lyell has found it in the pleistocene beds of Opslo 

 near Christiania, associated with Terebratula caput serpentis 

 (with which it now lives in Loch Fine) . His specimens exactly 

 resemble those obtained by Mr. MacAndrew, some of them how- 

 ever attaining a larger size, and being slightly broader in propor- 

 tion to the length and a very little more convex in form. Their 

 ribs are grouped in the same manner and as numerous. The 

 inner surface of the shell is exactly similar. The sculpture is 

 generally sharper, but this is also the case with the specimens of 

 Emarginula fissura from the same locality, and depends on fossi- 

 lization. The characters of the young shell, as exhibited by the 

 apex of the fossil specimens and compared with the fossil ex- 

 amples of E. fissura, are evident and distinct, consisting in the 

 greater length and more depressed form of the shell of E. crassa, 

 the obtuseness of the apex, the manner in which the ribs are 

 grouped, and the greater proximity of the striae between them ; 

 also the greater breadth of the fissural groove and the consequent 

 proportions of the slit. I mention these differences because Dr. 

 Beck told Mr. Lyell that he regarded the two species as one. 

 The Emarginula crassa would appear to be still living in the 

 Scandinavian seas, as Mr. Cuming has recent specimens from 

 Sweden. 



I offer the following diagnosis as a summary of the essential 

 characters : — 



Emarginula (crassa). Testa ovata, alba, convexa, costis longitudi- 



