76 CEYLON PEARL OYSTER REPORT. 



TRYGON UARNAK (FORSK.). 



This fish is called " Pullian tirikkai " in Tamil, which signifies " spotted ray," and 

 well describes its appearance. 



One specimen was obtained at Dutch Bay on January 6, 1905. The length of the 

 disc was 28 inches, the breadth 33 inches, and the tail was 56 inches long. 



Food. The stomach contents consisted exclusively of some score of small, swimming 

 crabs. 



Tylocephalum uarnak, n. sp. Plate V., figs. 85 and 86. 



A few examples were taken from the intestine of Trygon uarnak. The longest 

 measured some 35 millims. The number of segments is, however, small, varying from 

 30 to 40. The head, which is a little exaggerated in our figure (Plate V., fig. 86), 

 stands out like a button or knob at the end of the fine neck. The body is thickest 

 in the middle, some 0'7 millim. in breadth, the posterior extremely elongated 

 proglottides have a somewhat attenuated look. 



The head consists of an anterior lobe, resting on a squarish cushion ; the anterior lobe 

 or myzorhynchus seems to be fixed on to an extension borne by the cushion as though 

 on to a peg. This extension seems to be a thickened tissue, into which the longitudinal 

 muscles are inserted. The cushion is square, with suckers at each angle ; the anterior 

 lobe is separated from it by a simple contraction, not by a band as in Tylocephalum 

 pingue. There is a short neck. The proglottides show very early traces of reproductive 

 organs. The excretory pore is immense, a great round opening, more or less median ; 

 posteriorly it loses its firm outline, becomes crinkled, and is pushed a little aside by 

 the development of the uterus. The testes are scattered mostly at the anterior end 

 of each proglottis, and as the uterus develops the testes are pushed towards the 

 periphery and tend to disappear. The uterus is a long sac, constricted in the middle 

 by the reproductive pore like an old-fashioned " ring " purse. The posterior pro- 

 glottides are extremely long, at least 5 millims. in length, some ten times as long as 

 they are broad. None of the proglottides overlap. Their ends are flat and their sides 

 very nearly straight, or at most slightly bowed. 



The diagnosis of Tylocephalum uarnak is as follows : 



Length some 35 millims. Greatest breadth in middle region of body. Genital pore 

 very large, round and median. Testes scattered in anterior end of proglottis, pressed 

 outward by the growing uterus. The latter forms an anterior and posterior swollen 

 part united by a thinner portion. Number of segments 30 to 40. 



Habitat : The intestine of Trygon uarnak. This species also occurs in T. ivalga. 



Tetrarhynchus macroporus, n. sp. Plate V., figs. 87, 87 a and 876. 



These are fair-sized Tetrarhy rich ids, averaging about 25 millims. in length and 

 1 millim. in breadth. 

 The lateral lappets are small, each divided into two, each half corresponding with 



