42 FOSSIL FISHES OF THE ENGLISH CHALK. 



Genus PRIONOLEPIS, Egerton. 



Prionolepis, Egerton, in F. Dixou, G-eol. Sussex, 1850, p. 368. 



Aspidopleurus, Pictet and Humbert, Nouv. Eech. Poiss. Foss. Mt. Liban, 1866, p. 107. 



Apateopholis, A. S. Woodward, Proc. Zool. Soc, 1890 (1891), p. 634. 



Generic Characters.— }lead and trunk elongate, much laterally compressed. 

 Head acutely pointed, and the cranial roof exhibiting a median longitudinal depres- 

 sion, its lateral and occipital margins ornamented with ridges and tubercles of 

 ganoine. The conical teeth irregular in size, largest in the anterior part of the 

 mandible, small and obtuse behind. Operculum strengthened on the inner side by 

 a ridge extending horizontally backwards from the point of suspension ; preoper- 

 culum narrow and deep, its lower end bearing a slender, posteriorly directed spine. 

 Vertebrge about 45 in number, the centra at least as long as deep and constricted 

 mesially. Paired fins large, the pectorals not much larger than the pelvic pair, 

 which are opposed to the hinder part of the dorsal fin ; dorsal fin nearly median, 

 comprising from 16 to 20 rays; anal fin with slightly fewer raj's than the dorsal, 

 and much smaller ; caudal fin forked, with curved fulcral rays and stout, articulated, 

 undivided rays at its base both above and below. Dermal scutes in one deepened 

 series on the flank, each scute overlapping its fellow and traversed above by the 

 course of the lateral line. 



Type S'pecies. — Prionolepis angustiis, from the English Chalk. 



Remarks. — This genus is represented by nearly complete fishes from the LTpper 

 Cretaceous of Mount Lebanon originally made known under the names of Asjtido- 

 p)lenrus and Apateopholis. Technical descriptions of them are published in the 

 Catal. Foss. Fishes B. M., pt. iv, 1901, pp. 229—233. 



Prionolepis angustus, Egerton. Plate IX, figs. 4 — 9. 



1850. Prionolepis angustvs, Egerton, in Dixon, Gcol. Sussex, p. 3C8, pi. xxxii*, fig. 3. 



1888. Prionolepis angvsfus, A. S. Woodward, Proc. Geol. Assoc, vol. x, p. 306. 



1901. Prionolepis angustus, A. S. Woodward, Catal. Foss. Fishes B. M , pt. iv, p. 230. 



Tijijc. — Dermal scutes from zone of Holasfc.r sidxjlohosvs ; British Museum. 



Specific Characters. — Known only by the scutes of the flank. The largest 

 scutes about seven times as deep as broad, and the forwardly directed portion 

 above the lateral line comparatively short ; the hinder margin very regularly, 

 closely, and deeply i)ectinated ; the anterior portion eitlicr smooth or marked 

 with very feeble vertical rug«, except above the lateral line, where these rugae are 

 conspicuous. 



