SYSTEMATIC NOTES 389 



The longitudinal muscles are well developed and composed of thick fibres. In transverse section they 

 are collected in elongate bundles, separated from each other by muscular septa. The longitudinal 

 muscles in the cylindrical portion of the strobila are far better developed than those in the gravid 

 segments. 



The bundles in the anterior portion are thicker than in the gravid segments as shown in Figs. 24 

 and 25. This is probably owing to the pressure of the uterus as it becomes distended with eggs. 

 The circular muscles are exceedingly well developed, noticeably in the anterior portion of the 

 body. 



The testes are about 120 x 135 /x in transverse diameter and arranged in many layers in the cylindrical 

 part of the body. In the flattened portion they seem to be arranged in a single layer. The vas deferens 

 is well developed. The pear-shaped cirrus-sac is about 186X90/X in diameter. 



The genital atrium possesses a muscular modification in the form of a sucker. 



The ovary extends ventrally in the medullary parenchyma and is well developed. The vitelline gland 

 situated ventrally under the ovary is composed of compactly arranged cells. Neither the uterine 

 opening nor the rudiment of its duct has been found. The uterus is very well developed and gradually 

 pushes away other parts of the genital complex. The eggs are 75 X45//. in diameter and the embryo 

 54x36/^. The lateral hooks measure i8|a and the central 12/x. Yamaguti (1942) could not find any 

 hooks in his material. 



The excretory system is well developed and has transverse vessels connecting the two main 

 trunks. 



Trigonocotyle prudhoei sp.n. (Figs. 27-32). 



Hosts: Steno bredanensis, Lagenorhynchus obscurus, L. australis. 



Locality: 14 45' N, 18 34' W; East Falkland Islands (southernmost point of Bay of Harbours). 



The body is about 14-5 cm. in length and 1 mm. in width and composed of slightly overlapping 

 segments. The scolex, measuring from 1-5-2 mm. in width, is provided with four suckers bearing 

 fleshy protuberances. 



The longitudinal muscles are collected into bundles, with some indication of two layers dorsally, 

 when examined in transverse section. They seem to be separated by muscular septa. The circular 

 muscles are well developed. There are also dorso-ventral muscle fibres. 



The testes are not very numerous and occur mainly in the dorsal part of the segment. They 

 are about 120 ■: 60/x in transverse section, the longer axis being in the dorso-ventral plane. The 

 cirrus-sac is flask-shaped, about 32 x 15/tt in diameter, with thick muscular walls and a well-developed 

 cirrus. The vas deferens is well developed. Radiate muscles forming a sucker occur in the genital 

 atrium. 



The ovary is situated ventrally and extends laterally on both sides of the median line. The well- 

 developed vitelline gland is situated ventrally beneath the ovary. 



Neither a uterine pore nor the rudiment of a uterine duct have been observed. 



The eggs are 60 x 84/x. The inner membrane is 45 :■; 30 ju and the embryo 27 x 30 /x. The lateral pairs 

 of embryonic hooks measure 9^ and the central 6/x in length. 



The excretory system is well developed. 



This species differs mainly from other species of Trigonocotyle occurring in Cetacea in the form of 

 the serrate strobila and in the arrangement of the longitudinal muscles. It also differs in the number 

 and arrangement of the testes, these being less numerous and distributed dorsally. There are also 

 differences in the size of the eggs and in the length of the embryonic hooks as shown in Table 1 . 



