BR[TISH 



FOSSILS. 



Decade IX. Plate VII. Fig. 1. 



PLEUROPHOLIS. Gen. Nov. 



[Genus PLEUROPHOLIS. TrAeupa, the side ; <|)oAtr, a scute. Egerton. (Sub-kingdom 

 Vertebrata. Class Pisces. Order Goniolepidoti. Family Lepidostei. Sub-family 

 Lepidostei homocerci. 2nd Group, body elongated, more or less fusiform.) Caudal 

 fin forked ; dorsal fin'opposite the anal fin ; anal fin extended ; head small; body slender ; 

 scales of the flanks arranged in a single series.] 



Pleuropholis attenuatus. Morris. Cat. Brit. Foss., 1854. 



I propose the generic designation Fleuropholis for a small group 

 of fishes of diminutive size and limited geological range, but pos- 

 sessing characters singularly well defined and very distinct from 

 those of any genus of fossil fishes hitherto described. In the form 

 of the head, the position of the mouth, and general outline of the 

 body, they somewhat resemble a small Thrissopa or Leptolepis. The 

 arrangement of the fins also corresponds to some extent with that 

 of those organs in the former genus. The characters of the tail 

 resemble those of Ophiopsis. The dermal peculiarities, however, are 

 so remarkable that they forbid the association of Pleuropholis with 

 any known genus. If we except the isolated family of the Acan- 

 thodei, the multiplication of the scales in the dorso-ventral series is 

 greatest in the genera Pachycormus, JSndactis, and Gosmolepis. 

 In the latter we find not less than sixty scales in each series on the 

 anterior and middle regions of the trunk. In Nothosomus the 

 number is reduced to eight, and in the sauroid genus Aspidorhyn- 

 chus the flanks are protected by large scutes, the dorso-ventral series 

 being completed above and below by a few scales of much smaller 

 dimensions. These characters are subject to occasional variations 

 in the latter genus, and the single scutes are sometimes replaced by 

 two or three scales. In Pleuropholis the dorso-ventral series are 

 also composed of a single row of scutes, completed above and below 

 by a few small scales, the latter being more numerous in the caudal 

 region. In this respect it resembles the cretaceous genus Priono- 

 [ix. vii.] 9 H 



