9() DB TRAILL ON FOSSIL FISHES FOUND IN ORKNEY. 



The character of the species are drawn by this philosophic inquirer princi- 

 pally from the general form and size of the fish, the external surface of its 

 scales, then- relative size on the different parts of its body, the nature of the 

 rays of the fins, especially of the first ray, the form and size of the opercula or 

 gill-covers, and of the bones of the head. 



When M. AGASSIZ first visited this kingdom, I submitted to him a consider- 

 able collection, which I had made, of the fossil fishes from the old red-sandstone 

 formation of Orkney ; among which he instantly recognised several new species, 

 and at least one genus, to him then totally unknown, to which he assigned the 

 generic name of DIPLOPTERUS ; but the species has remained to this day unde- 

 scribed. I have lately understood that a Diplopterus has been found in another 

 part of Scotland, and one in Ireland ; but whether identical with the Orkney spe- 

 cies I am unable to decide. Assuming to myself the privilege usually conceded 

 to the finder of a new species, and desirous of connecting with my country the 

 name of the celebrated naturalist, who has done so much to elucidate its Fossil 

 Ichthyology, I some time ago proposed to designate this species DIPLOPTERUS 

 AGASSIS, under which name I have already sent specimens of it to several Geolo- 

 gical Collections ; and now beg to present a specimen of it to the Royal Society, 

 along with some other fossil fishes from the same county. 



During the late visit of the philosopher of Neufchatel to this country, I was 

 enabled to shew him an additional series of specimens from Orkney ; and he has 

 now ascertained that my collection contains the following fossil species from those 

 islands : 



1. Osteolepis Macrolepidotus. 



2. Microlepidotus. 



3. Cheirolepis Traillii. 



4. Cheiracanthus Minor. 



5. Diplopterus Agassis. 



6. Diplocanthus Crassissimus. 



7. Dipterus Macrolepidotus. 



8. Platygnathus Paucidens. 



9. Coccosteus Latus, 

 10. Pterichthys Milleri? 



In a short memoir which was read to the Royal Society of Edinburgh in 

 1833, and to the British Association in 1834, I stated that fossil fishes Avere found 

 in great number and finely preserved in a quarry at Skaitt, on the western coast 

 of Pomona, the largest of the Orkney Islands, at about two miles to the north of 

 a granite ridge which traverses part of the island for six miles. This, with a 

 small patch in the adjacent isle of Grsemsey, is the only granite in Orkney. 



