BRITISH FOSSILS. 



Decade VI. PlxIte V. 



PHOLIDOPHOEUS CRENULATUS. 



[Genus PHOLIDOPHORUS. Agassiz. (Sub-kingdom Vertebrata. Class Pisces. 

 Order Goniolepidoti. Family Lepidostei. Sub-family Lepidostei homocerei. 2d Group. 

 Body elongated, more or less fusiform.) Dorsal fin small, opposite theventrals; caudal 

 fin forked ; the lobes equal ; the base of the upper lobe invested with scales ; teeth 

 villiform.*] 



Synonym. — Pholidophorus crenulatus, Egerton, Proceedings of Geol. 

 Soc. 1843, p. 184. 



Description. — This is a rare but well-marked species of Pholi- 

 dophorus belonging to the group of which Pholidophorus Bechei 

 may be considered the type. In form and proportions it resembles 

 Pholidophorus latiusculus, but the characters of the scales are 

 wholly dissimilar. Of the Pholidophori of the lias, described by 

 Agassiz, one only, namely P. limhatus, has serrated scales. This 

 structure obtains also in Pholidophorus crenulatus, under descrip- 

 tion, but it is the only feature common to the two species. The 

 head is either crushed or wanting in the only specimens I have 

 seen. It seems to have been smaller in proportion to the entire 

 length of the fish than in P. Bechei, P. onychius, and P. limhatus. 

 The coracoid bone is traversed obliquely along its anterior curva- 

 ture with rounded plaits. The pectoral fins are large, composed of 

 about 22 rays, slender, and dichotomous in their distal portions. 

 The anal fin is small. The caudal fin contains from 28 to 30 rays, 

 with short articulations. The lower lobe is considerably larger 

 than the upper one. The base of the upper lobe is invested with 

 scales, and its upper margin protected by a series of strong imbri- 

 cated fulcral scales ; these increase in length as they succeed each 

 other, until they almost rival the true marginal rays of the lower 

 lobe. The scales present two very distinctive characters. The 

 anterior portion or base of the scale is marked by a series of parallel, 

 vertical ridges, extending backwards as far as the articulating pro- 



[VI. v.] 



* Poiss. Foss., vol. ii. p. 9. 



