the Primari/ Rocks and the Oolitic Series in the North of Scotland. ]4S 



Since the specimens here described were sent to Paris, more perfect 

 remains have been discovered ; and from a careful study of these, M. Va- 

 lenciennes and Mr. Pentland have not only confirmed the opinion of Baron 

 Cuvier, but have enabled us to add the following- details. 



The specimens of the order above mentioned belong; to two new o-enera ; 

 and the first of these it is proposed, on account of the double dorsal fin, to 

 call Dipterus. Of this there are the following species. 



The first and most abundant* is recognized by the shortness of the anal 

 fin, which does not exceed half the length of the inferior lobe of the caudal 

 fin. This species, which may be named Dipterus brach^pi/gopterus, seems to 

 have occasionally attained a considerable size, the scales measuring rather 

 more than the sixth part of an inch. 



A second speciesf, which may be named Dipterus macropT/gopterus, is equal 

 in size to the preceding; from which, however, it is easily distinguished by the 

 length of the anal fin, which is very acutely pointed, and is prolonged beneath 

 the caudal fin almost as far as the inferior lobe. The scales of this species are 

 much larger than those above described, being one-fourth of an inch broad. 



A third species appears never to have attained the size of those above de- 

 scribed, although it is remarkable for the much greater magnitude of its scales. 

 The anal fin, although long, never equals that of Dipterus macropi/gopterus, 

 from which, as well as from D. brachypygopterus. it further differs in having- 

 a rounded tail. 



A fourth;}: and much smaller species has been named Dipterus Valencien- 

 nesii, after the acute observer who first distinguished its characters. 



Among the fragments is one specimen consisting of many large scales §, show- 

 ing nothing of the shape of the head, nor any traces of the fins, but exhibiting, 

 with another specimen ||, fragments of what appear to be bones of the head 

 and opercula. It is therefore impossible to determine with certainty whether 

 the remains of this fish are those of a species of Dipterus : analogy, however, 

 would lead to that conclusion ; for the scales are round, imbricated, and covered 

 with granulations, in all of which characters it is similar to the other Dipteri. 

 Until new observations shall afford materials for pronouncing decidedly on the 

 genus to which this fish belongs, it may be named, provisionally, Dipterus ma- 

 crolcpidotus. 



The specimen represented in Plate XVI. fig. 2. appears to be a young in- 

 dividual of the same species. 



The second genus of fish discovered in Caithness f, approaches to the cha- 



• Plate XVII. fig. 1. 2. 3. t Plate XV. fig. 1.2. 3. 



X Plate XVI. fig. 1.3. § Plate XVI. fig. 4. II Plate XVI. fig. 5. 



11 At Widel quarries some miles north of Banniskirk. 



