﻿RITTZODONTIDiE. 



3(51 



1875. Tristichopterus alatus, R. H. Traquair, Proc. Roy. Soc. Edinb. 



vol. viii. p. 513. 

 1875. Tristichopterus alatus, R. H. Traquair, Trans. Roy. Soc. Edinb. 



vol. xxvii. p. 383, pi. xxxii. 



Type. Imperfect fishes ; Museum of Practical Geology and British 

 Museum. 



The type species, attaining a length of about 0*3. Maximum 

 depth of trunk nearly equal to the length of the head, and contained 

 about six and a half times in the total length. Head somewhat 

 longer than deep : operculum deeper than broad ; all the bones 

 ornamented with granulations, more or less fused into short tor- 

 tuous rugse. Pelvic fins about three quarters the size of the pec- 

 torals, arising immediately behind the middle point of the trunk, 

 and opposed to the somewhat smaller anterior dorsal fin ; posterior 

 dorsal and anal fins of nearly equal size, deeper than broad, and 

 much larger than the anterior dorsal ; length of caudal fin much 

 less than its maximum depth. Scale-ornament very fine and closely 

 arranged. 



Form. &f Loc. Lower Old Red Sandstone : Caithness. 



All the specimens mentioned below are comprised in the Peach 

 Collection, and were obtained from the neighbourhood of John 

 o' Groats. 



42396. Counterpart of one of the type specimens figured by Egerton, 



loc. cit. pi. v. 



42397. Fish, showing well-preserved caudal region, noticed by 



Traquair, loc. cit. 1875, p. 384. 



42398. Imperfect head and anterior part of abdominal region, with 



right pectoral fin. The tubercular and partly rugose 

 ornamentation of the head-bones is distinct, and portions 

 of the broad, ring-shaped vertebras occur. 



42406. Imperfect trunk with part of the head and large portions 



of the fins. 



42407. Part of the squamation of a large fish, with remains of the 



axial endoskeleton and some of the fin-supports. 



Genus EUSTHENOPTERON, Whiteaves. 



[Canadian Naturalist, n. s. vol. x. 1881, p. 30.] 



Body much depressed anteriorly, with round or ovoid scales, of 

 which the exposed portion is ornamented with granulations and 

 antero-posteriorly directed rugae. Head-bones more or less tuber- 



