FOSSIL AND RECENT 139 



they are inserted nearer to the distal end of the arch. Short epipleural intermusculars 

 are associated with the first 73 parapophyses. Anteriorly there are 11 sigmoid 

 supraneurals. The anterior members of the series are larger than those posteriorly. 



Median fins. The dorsal fin is elongate, equal in length to half the standard length 

 and composed of 58-60 fin-rays. The first four fin-rays are unsegmented and un- 

 branched. The fifth is segmented and the sixth and those succeeding it are branched 

 at least twice. The fin-rays are supported by 56-58 pterygiophores. Most of the 

 pterygiophores are composed of separately ossified proximal, middle and distal 

 radials but the first two, which between them support four fin-rays, are formed by a 

 large compound radial and a separately ossified distal radial. 



The anal fin originates beneath the seventy-fifth vertebra and is composed of 

 12 fin-rays of which the first three are unbranched and unsegmented, the next two 

 are segmented but unbranched while the rest are both segmented and branched. 



The caudal fin is deeply forked and the margin of each lobe is rounded. Eight 

 centra, two ural and six preural, are involved in the support of caudal fin-rays. The 

 ural centra are as long as deep, sharply upturned and show little or no ornamentation. 

 The neural spines of the third to sixth and the haemal spines of the first to sixth 

 preural centra are longer and stouter than their anterior counterparts. These 

 structures also show the development of median wings basally. The neural spine 

 of the second preural centrum varies ; Gosline (1961) records a complete neural 

 spine but in the four specimens I examined there is only a half spine, as in the 

 specimen of P. belloci illustrated by Monod (1968). The neural arch of the first 

 preural centrum is represented by a thin ossified structure above which there is a 

 broad plate of cartilage which lies between the halves of the first uroneural posteriorly. 



There are two narrow uroneurals. The first is long and the expanded proximal 

 end partially covers the first preural centrum. The second uroneural is shorter, 

 fails to overlap any centrum and extends beyond the distal tip of the first. Such a 

 uroneural disposition is typical for more advanced albuloids. 



There are six hypurals. The first and second hypurals articulate with the first 

 ural centrum, the third and fourth are associated with the second ural centrum, 

 and the fifth and sixth lie free. The base of the third hypural is expanded and 

 partially encircles the centrum. The large gap between the second and third hypurals 

 is a typical feature of the pterothrissid caudal skeleton. The epurals are represented 

 by three splint-like elements forming a graded series. 



As usual in ' lower ' teleosts there are 19 principal caudal fin-rays. The bases of 

 the innermost principal rays are not expanded and do not overlap the hypurals to 

 any significant degree (cf. elopoids). There are 14-16 basal fulcra dorsally and 7-8 

 ventrally. The anterior members of both series lie free in the musculature. 



Squamation. The body is covered with cycloid scales. There are approximately 

 100 in the lateral line series while the transverse count at the origin of the dorsal fin 

 is 7 above and 8 below the lateral line. Precise counts are difficult because of the 

 condition of the specimens examined. Large axillary scales are associated with the 

 pectoral and pelvic fins. 



Each scale is generally rounded but has a straight anterior margin. The posterior 

 margin is thin and frequently split. Lateral line scales, apart from a slight anterior 



