60 CEYLON PEARL OYSTER REPORT. 



LINTON'S species, T. pingue. The last proglottides were equally rounded, and 

 contained a uterus full of ova. 



The diagnosis of Tylocephalum dierama is as follows : 



Length between 20 millims. and 30 millims. Proglottides with very overhanging 

 posterior borders. The body is flattened. 



Habitat : Myliobo.tis rnaculata, in the intestine. 



KHINOPTERA JAVANICA (MtlLLER and HENLE). 



" Of the two species of Rhinoptera recorded from Indian waters, R. javanica is 

 the fish known as ' Valvadi tirikkai ' to Tamil fishermen. From the accounts 

 received of a very closely allied but much larger species which goes by the name of 

 ' Mundeikanni tirikkai,' and which I have not yet seen, I have no doubt that it is 

 the second Indian species of Rhinoptera, R. adspersa (MULLER and HENLE). 



" Prior to the present, ' Valvadi tirikkai ' has been wrongly identified with 

 Trygon uarnak. Mr. H. SULLIVAN THOMAS (" Report on Pearl Fisheries and Chank 

 Fisheries, 1884," Madras, 1884, p. 17) was the first in this error, and until the 

 present his identification h.as been followed. During my recent stay of several weeks' 

 duration at the fishing station of Dutch Bay I had exceptional opportunity to 

 examine large numbers of Bays, and to learn the native names. Before I had seen 

 any specimen of ' Valvadi,' by enquiry from many different sources I learned that its 

 characteristics were entirely those of a Rhinoptera. All the men I cross-examined 

 concerning 'Valvadi' laid stress on the snout being truncate; the skin smooth, 

 without tubercles ; and the teeth ' stony.' I showed them sketches of Kays, and in 

 each case they recognised a woodcut of the dental armature of R. javanica as 

 identical with that of their 'Valvadi.' They all agreed that this is an oyster-eating 

 species, and SULLIVAN THOMAS' statement that the ' Valvadi ' devours pearl oysters 

 is correct, but not his linking of it with the name Trygon uarnak. 



" Later I had the opportunity to dissect both R. javanica and T. uarnak^ The 

 former agreed in every particular with the description of the oyster-eating ' Valvadi,' 

 whereas the latter had the median region of the dorsum tuberculated, a pointed 

 snout, and a dental apparatus wholly unfitted for devouring oysters of large size. 

 The teeth were comparatively weak and closely approximated in form and arrange- 

 ment with those of the Crustacean-eating Trygon ivalga. The stomach contents in 

 T. uarnak were also Crustaceans, consisting of some scores of the young of a small 

 swimming crab. It goes by the distinctive Tamil name of ' Pull i an tirikkai,' i.e., 

 ' spotted Bay.' T. uarnak is thus the ' Pullian tirikkai ' of the natives. 



" Be verting to R. javanica, the dissection of three specimens showed the food, as 

 evidenced by the stomach contents, to be exclusively molluscan. They consisted 

 almost wholly of Lamellibranch fragments.* 



h The shells from the stomach of this specimen were kindly examined by Mr. E. A. SMITH and 

 Mr. B. B. WooDWAKD, of the British Museum, but the fragments were too small to be identified. 



