PLEUROPHOLIS. 117 



usually slender and normal, becoming very small before disappearing distally ; but 

 in one specimen (B.M. no. P. 6304) the fulcra of the anal fin bear expansions like 

 those already described on the pectoral fulcra. The caudal fin is nearly complete 

 in the type specimen, displaying its 16 rays, of which 4 in the middle are well 

 spaced. Its deeply overlapping fulcra are very slender, and become minute distally 

 before they disappear. The upper caudal lobe of the. body is prominent. 



As shown by the type specimen, all the scales are smooth, without posterior 

 serrations, and they are arranged in about 40 regular transverse series. All, 

 except those near the end of the tail, are strengthened within by a broad vertical 

 ridge, and united by a peg-and-socket articulation. The deepened flank-scale 

 occurs in more than 80 of these series before it begins to subdivide on the caudal 

 pedicle, being from four to five times as deep as its complete width in the front 

 part of the abdominal region, and gradually becoming not much more than twice 

 as deep as wide before subdivision on the caudal region. Each scale exhibits a 

 slightly sigmoidal bend, and its lower end is truncated, while its upper end tapers 

 a little as it curves forwards. Above each large flank-scale there are two other 

 scales, of which the lower at least is deeper than wide ; and there seem to be 

 indications of the large flattened dorsal ridge-scales, such as are well seen in an 

 example of another species of Pleuropholis from the Lithographic Stone of Cirin, 

 Ain, France, in the British Museum (no. P. 4691a). The foremost upper scale is 

 traversed by the slime-canal of the lateral line, which then passes down the second 

 deepened flank-scale, and continues its course along a row of nearly square scales 

 adjacent to the lower ends of the deepened flank-scales. Usually in the fossils the 

 tubular excavation of the lateral line is exposed, but Avhen a scale is perfect its 

 only mark is a faint ridge. In the abdominal region there are four scales, wider 

 than deep, beneath that of the lateral line, the lowest apparently forming the 

 ventral ridge. At the base of the anal fin one row occurs beneath the lateral line, 

 while in the caudal region beyond there seem to be three rows. On the caudal 

 pedicle the deepened flank-scale is divided by a transverse suture into two, then 

 into three scales, and the terminal scales are very small and rhombic. The lateral 

 line ends abruptly at the insertion of the lowest of the four spaced caudal fin-rays. 

 The acutely pointed and deeply overlapping caudal ridge-scales which pass into 

 the fulcra of the caudal fin above and below are only moderately enlarged. 



Immature Fish (PL XXII, tig. 8). — The immature Pleuropholi*, only about 

 3 cm. in length, shown enlarged in PI. XXII, fig. 8, has a relatively large head ; 

 but it may well be the fry of the species now described. It still lacks all the 

 scales except the middle portion of those of the flank, and thus displays the 

 internal skeleton. The remains of the head are much broken by crushing, but 

 the curved parasphenoid is distinct in side view, and the relatively small mandible 

 is observable. The course of the persistent notochord is indicated by a vacant 

 space, but the neural and haamal arches are well calcified. In the abdominal 



