DERCETIS. 65 



Genus DERCETIS, Agassiz. 



Dercetis, L. Agassiz, Neues Jahrb., 1834, p. 389. 



Generic Characters. — Vertebras between 50 and 60 in number. Dorsal fin 

 occupying the greater part of the back, and anal fin opposed to its hinder portion ; 

 caudal fin forked. Dermal scutes considerably expanded, and the adjoining longi- 

 tudinal series often in contact; a paired series along the dorsal and ventral 

 borders, and another along the lateral line ; no intermediate squamation. 



Type Species. — Dercetis scutatus (L. Agassiz, Neues Jahrb., 1834, p. 390, and 

 A. S. Woodward, Catal. Foss. Fishes B. M., pt. iv, 1901, p. 172), from the Upper 

 Cretaceous of Baumberg, Westphalia. 



Remarks. — -The two species from the English Chalk provisionally referred to 

 this genus, are only known by fragmentary remains which arc insufficient for 

 exact generic determination. 



1. Dercetis latiscutatus, sp. nov. 



Type. — Middle portion of trunk from a Turonian zone ; Willett Collection, 

 Brighton Museum. 



Specific Characters. — Dermal scutes short and broad, angularly bent at the 

 middle, which is not much produced forwards. The outer face of the scutes orna- 

 mented in front with tubercles, which are sometimes arranged in radiating rows; 

 behind with reticulating ridges, which tend towards a direction at right angles to 

 the posterior border. Dorso-lateral scutes of the middle of the trunk about equal 

 in size to those of the lateral line, with which they are in contact and inter digitate. 



Description of Specimens. — The type specimen comprises a fragment of the head 

 and remains of the middle portion of the trunk (PL XV, fig. 1). It is insufficient 

 to determine the exact proportions of the fish. 



The head, as indicated by the type and by a smaller specimen in the British 

 Museum (no. P. 3847) evidently of the same species, must have been closely 

 similar to that of Leptotrachelus elongatus (described below, p. 70). Its inter- 

 orbital region seems to have been slightly wider than in the latter species, and the 

 antero-lateral portions of the frontal bones are ornamented with a few ridges which 

 radiate forwards. In B. M. no. P. 3847 there are the usual slender, clustered 

 teeth. 



The dermal scutes encircling the middle of the trunk clearly form a continuous 



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