138 



ELOPIFORM FISHES 



ep1-3 



nsp pu 



h 3-6 



-u1-2 



h1-2 



Fig. 68. Pterothrissus gissu Hilgendorf. Caudal skeleton in left lateral view. 

 Arrows indicate upper and lower principal caudal fin-rays. 



Pelvic girdle and fin. The pelvic fin originates mid- way between the snout and the 

 caudal peduncle. The fin is supported by a triangular pelvic bone. A narrow band 

 of cartilage forms a cap along the posterior margin of the pelvic bone. Only the 

 innermost pelvic radial is ossified. There are io pelvic fin-rays, the outermost 

 unbranched and the third apparently the longest. A large pelvic splint is associated 

 with the base of the upper half of the outermost (the first) fin-ray. 



Vertebral column. Of the 107 vertebrae 35 are caudal. Each centrum is amphi- 

 coelous and pierced for the passage of the constricted notochord. Most centra 

 throughout the column are marginally deeper than long but the first sixteen and the 

 posterior three or four are almost twice as deep as long. The lateral surface of each 

 centrum is marked by several longitudinal ridges. 



The neural arches are autogenous. Those upon the anterior 45 centra are ex- 

 panded distally and bear narrow neural spines. Throughout the abdominal region 

 the spines are represented by separate lateral halves. Short, stout, autogenous 

 parapophyses are found throughout the abdominal region. Those posteriorly are 

 somewhat longer than those anteriorly. The first complete haemal arch and spine 

 occurs on the seventy-sixth centrum. 



The pleural ribs are short and slender and partially encircle the abdominal cavity. 

 Epineural intermuscular bones are associated with the first 67 neural arches. Those 

 associated with the first 49 are attached to the base of the neural arch, but thereafter 



