PHOLIDOPHORUS. 107 



The longitudinal slime-canal is marked by a few pores. Remains of the supra- 

 temporal and post-temporal plates behind are also closely and finely tuberculated. 



The opercular apparatus is shown in inner view in PI. XXI, fig. 5. The 

 operculum (op.) is narrow above owing to the rounding of the postero-superior 

 angle, and its depth to the middle of the lower border equals its maximum width. 

 The large suboperculum (sop.) is half as deep as the operculum, and bears the 

 usual antero-superior prominence. The preoperculum is much expanded at its 

 angle, and the interoperculum is relatively small. The opercular bones and 

 remains of branchiostegal rays in the type specimen are finely granulated. 



Although the neural and haemal arches in the vertebral axis are well ossified, 

 the centra must have been extremely delicate, for there is scarcely a trace of 

 them in the known specimens. 



The scales are regularly arranged in about 45 transverse series ; and there 

 are 16 scales in the series above the origin of the pelvic fins, the ninth from 

 below being traversed by the slime-canal of the lateral line. On the flattened 

 ventral surface of the abdominal region they are rhombic and nearly equilateral, 

 deeply overlapping, and ornamented in their exposed portion with fine radiating 

 ridges, which end behind in serrations and pass forwards into tuberculations. 

 On the lateral edge of this ventral area each scale is bent along its antero- 

 posterior diagonal. On the flank. of the abdominal region the dorsal and ventral 

 scales are also rhombic and nearly equilateral ; but in each series eight or nine 

 scales are deeper than broad, the deepest being those of the lateral line and the 

 three horizontal rows beneath it. In the anterior series (PI. XXI, fig. 5a) these 

 scales are very deeply overlapping, and all are conspicuously ornamented with the 

 fine radiating ridges, which end at the hinder border in serrations. On the 

 principal scales the ridges cover nearly the whole of the exposed surface, leaving 

 only a small triangular rugose or tuberculated area near the lower border ; but on 

 most of the abdominal scales they pass forwards into tuberculations or rugae. 

 Further back and on the caudal region (fig. 56) the fine radiating ridges gradually 

 become shorter, leaving the rest of the scale smooth ; until towards the end of 

 the caudal pedicle both ridges and serrations disappear. In the anterior part of 

 the abdominal region (PI. XXI, fig. 5a) the lateral line is marked only by a slight 

 ridge and posterior notch on the scale ; but further back and in the caudal region 

 (fig. 56) it opens by a prominent perforation on most of the scales. In all the 

 scales of the abdominal region the peg-and-socket articulation is large, while the 

 inner rib is broad and prominent (PI. XXI, fig. 6a) ; in the hinder half of 

 the caudal region (fig. 66) both the articulation and the inner rib disappear. 

 There are enlarged scales round the anus near the origin of the anal fin. 



The position of the fins is shown in the type specimen, but they are imperfect 

 in all known specimens. The pectoral fins, which comprise about 18 rays, are not 

 much more elevated than the pelvic fins, which comprise 10 or 12 rays and are 



