TRISTICHOPTERUS ALATUS. 



55 



suggests the idea of a Dipterian fish with Ctenoid scales. If the 

 family is proved to be well founded, the title Ctenoclo-dipterini 

 would be preferable. The genera Cemtodus of Agassiz, and Gon- 

 chodus and Chirodus of M'Coy are referred by Pander to this 

 family. The absence of all evidence as to the dental apparatus of 

 Tristichopterus is much to be regretted. On other points the 

 affinities between this genus and Dipteriis are so striking that they 

 cannot be classified in separate families. 



Locality. — At the meeting of the British Association at Aberdeen 

 in 1858, Mr. Peach read a short notice of several new forms of 

 fossil fishes discovered by himself in the north of Scotland. The 

 subject of the present Memoir is thus alluded to : The great 

 " interest attaching to the next arises from its having a short 

 " vertebral column runniog from head to tail, and also strong in- 



ternal supports to the fin-rays. Whether these and the vertebral 

 " column are of bone is still an open question. The scales are 

 " large and coarse ; it is about ten inches in length ; and came from 

 " the red and blistered sandstones near John o'Groat's House." The 

 second specimen, contributing materially to the knowledge of the 

 genus, is not mentioned by Mr. Peach. Both these specimens now 

 form part of the collection in the Museum of Practical Geology. 



Explanation of Plates IV. and V= 

 Plate IV. 



Fig. 1. Tristichopterus alatus, size of nature. 

 Fig. 2. Structure of the tail, magnified. 



Plate Y. 



Fig. 1. Tristichopterus alatus, size of nature. 



Fig. 2. Scale of the flank, magnified. 



Fig. 3. Scale from the lateral line, magnified. 



P. DE M. Grey Egertok 



Oulton Park, Nov. 15, 1860. 



