2 



BRITISH FOSSILS. 



sufficient to distinguish the species from all others. Very fine 

 specimens have recently been found which prove this character to be 

 constant and uniform ; so much so, that a single scale could at once 

 be recognized without fear of error. The subject of this article 

 constitutes a second species, also from Swanage, and more nearly 

 allied to Pholidophorus ornatus than to any other species. The 

 distinctive feature most easily appreciable is the greater depth of 

 the body as compared with the length ; there are also differences 

 in the form and ornamentation of the scales, which will be de- 

 scribed in the sequel. The specimen selected for representation 

 measures 6|- inches from the snout to the commencement of the 

 tail. The depth of the body from the anterior limb of the dorsal 

 fin to the insertion of the ventral fin, is 2| inches ; and from the 

 nape to the insertion of the pectoral fin, 2 inches. These relative 

 dimensions in a specimen of Pholidophorus ornatus, 6 inches in 

 length, are only 1^ inch for the former, and 1^ inch for the latter, 

 a difference too remarkable to be attributed either to sexual pecu- 

 liarities or to accidental circumstances. The head measures 1| inch 

 in length, and If in depth, while in the allied species these dimen- 

 sions are reversed, the length being greater than the depth. The 

 bones of the head are prettily ornamented with groups of granules 

 arranged in a variety of patterns. They are most numerous on the 

 frontals and pre-frontals. This granular character occurs also on the 

 branchiostegous rays, the opercular flap, and the scales extending 

 from. the occiput to the dorsal fin. The operculum is of moderate 

 size, but the sub-operculum is enormously developed in the vertical 

 direction. The granular character is less prominent on these bones 

 than on the other parts of the head. The dorsal fin is placed nearer 

 the head than is the case in Fholidophorus ornatus. It is com- 

 posed of about a dozen rays, of which the first four are short and 

 single, the remaining ones broad with frequent transvere articula- 

 tions, and bifurcate extremities. The pectoral fins are of moderate 

 size, and contain about 18 rays, all slender except the first, which 

 is thick and strong. The distance between these and the ventral 

 fins is less than in Pholidophorus ornatus. The latter organs 

 contain each from 10 to 12 rays. The exterior one has an orna- 

 mental border of oblique osselets, the succeeding ones are stronger 

 than those of the pectoral fin, and have few transverse articulations, 

 these being restricted to the distal, bifurcate, extremities. The anal 

 fin is equidistant from the insertion of the ventrals and the com- 

 mencement of the tail. Only a trace of it remains. The caudal fin 

 is also deficient. The lateral line is nearly horizontal. The scales 



