BRITISH FOSSILS. 



s 



Plate VII. Fig. 6—8. 

 Pholidophorus nitidus. Sp. Nov. 



Description. — Associated with the preceding group of fish, two 

 specimens were found, which although very imperfect, incontestably 

 constitute a new and distinct species Pholidophorus, Among 

 the numerous members of this overcharged genus, many of which 

 are remarkable for graceful forms and proportions, none can vie 

 with the subject of this memoir for symmetry and elegance. As 

 compared with Pholidophorus Higginsi, the head is smaller, the 

 body more slender, and the shape and proportions of the scales 

 dissimilar. The imperfection of the specimens precludes a very de- 

 tailed description of the species, at the same time enough remains 

 to establish specific characters which may be safely relied on. One 

 specimen, belonging to the Bristol Institution, shows the impression 

 of a portion of the head and the opercular apparatus. It was 

 evidently small in relation to the body, and the surface of the bones 

 was smooth and highly polished. The other specimen, of which a re- 

 presentation is given double the natural size, belongs to Mr. Higgins. 

 It shows the greater part of the trunk, together with the dorsal 

 and one ventral fin. These are situated opposite each other, and 

 are composed of a small number of fine fin rays. The scales are 

 beautifully preserved, without either dislocation or fracture, and 

 present the following characters. The principal series, or that 

 constituting the lateral line, contains the largest scales. They are 

 oblong in form, being considerably higher than they are wide. The 

 posterior angles are slightly rounded. The central area of each 

 scale is traversed by a ridge indicating the course of the mucous 

 tube, and in addition to the notch at the posterior margin for the 

 exudation of the lubricating secretion, there is also on each scale a 

 foramen on the upper margin of the tube (Plate 7. fig. 7.) The row 

 of scales immediately below the lateral line is next in importance. 

 In this set the vertical diameter is much reduced, and in the suc- 

 ceeding rows, about four in number, this diminution is progressive, 

 the scales in the vicinity of the ventral fins being nearly equilateral. 

 Above the late.ral line one row of large scales occurs, and this is 

 succeeded by four or five rows in which not only are the dimensions 

 exceedingly reduced, but the posterior margins, by the elongation 

 of the lower angles, assume the lozenge form. They are all highly 

 lustrous, and the only irregularities of surface discernable with a 

 pocket lens are the concentric undulations recording the successive 

 growths of the scales. 



[VIIL vii.] 8 H 2 



