FOSSIL AND RECENT 179 



The pelvic fin originates beneath the posterior half of the dorsal fin. The pelvic 

 fin is made up of 9-10 rays, the outermost being both the longest and the only 

 unbranched member of the series. Associated with the base of the upper half of 

 the outer ray there is a large pelvic splint bone. The anterior end of this splint is 

 curved dorsally and lies free from the fin-ray bases. 



Vertebral column. One specimen, B.M.N.H. P.9162, is sufficiently well preserved 

 for a vertebral count to be made. This specimen has a total of 66 preural vertebrae 

 of which approximately 23 are caudal. 



Each centrum is deeper than long. Those of the anterior abdominal region are 

 considerably deeper relative to their length than those of the caudal region. The 

 centra are marked laterally by four to six longitudinal grooves separated by ridges. 



The neural arches are autogenous throughout the column. In the anterior 

 abdominal region the neural arches are expanded distally but in the posterior ab- 

 dominal and caudal region such expansions are not seen. The neural spines of the 

 anterior abdominal region are fine, straight and the paired halves remain separate. 

 Posteriorly the spines of either side are fused to form a median structure which 

 exhibits a slight backward curvature. The posterior neural spines are somewhat 

 modified to support the caudal fin-rays. 



The parapophyses are autogenous. Throughout most of the abdominal region 

 they are represented by small knobs lodged in cup-shaped depressions in the anterior 

 half of the centra. The posterior five or six parapophyses are somewhat longer, 

 the last being the longest and bearing a correspondingly shorter pleural rib. 



Each pleural rib is fine, slightly curved and incompletely encircles the abdominal 

 cavity, substantiating the view that this fish had a rounded body. Except pos- 

 teriorly, where the ribs are borne solely by the lengthened parapophyses, the articula- 

 tion of the ribs is shared between the parapophysis and the centrum. 



The haemal arches are inserted into depressions in the centra. Distally the arches 

 bear slightly curved haemal spines. The posterior five are modified to support the 

 caudal rays. 



There are 11-12 supraneurals associated with the first 17-18 neural spines. Each 

 supraneural is sigmoid in shape and they form a graded series from large and broad 

 anteriorly to small and narrow posteriorly. 



Epineurals are found throughout the column. Anteriorly they are attached to 

 the posterior margin of the neural arch/spine junction. In the posterior part of the 

 column they are often displaced and in life probably lay free in the myocommata. 



Epipleurals are also present throughout the column. In the abdominal region 

 they were closely applied to the parapophyses but throughout the caudal region they 

 lay free. The epipleurals in the anterior caudal region show forked bases. 



Median fins. The dorsal fin is relatively long based, the base length being equal 

 to 28 per cent of the standard length. The origin of the fin lies near the occiput and 

 the occiput-origin distance is considerably less than the distance from the termina- 

 tion of the fin to the caudal peduncle, a feature previously noted by Woodward 

 (1901 : 16). 



The dorsal fin is composed of 24-25 rays. Davis (1887 : 560, pi. 31, fig. 2) states that 

 there are 32 rays but his illustration does not support such a high count. Woodward 



