ig.i6.] 



Fauna of the Chilka Lake : Fish. 



409 



1889. Trygon imbricata, Day, Faun. Brit. Ind., Fish., I, p. 52. 



1909. Trygon imbricata, Annandale, Mem. Ind. Mus., II, p. 32, text-fig. 6, pi. iii, fig. 5. 



1913. Dasybatus imbricatus, Garman, Mem. Mus. Comp. Zool. (Harvard), XXXVI, p. 379. 



This small Trygon is very common all over the lake-system at all times of the year 

 and breeds in the lake. There are three adult specimens in the collection ; one was 

 obtained off Samal Island (22-IX-13), one at Rambha (February, 1914) and the other 

 at Balugaon (5-1-15). Besides these, there are four embryos two of which are small 

 males and the other two still smaller females. The female embryos are slightly longer 

 than broad, whereas in the males the disk is almost as broad as long. The length of 

 the tail in the male embryos is nearly double the length of the disk, whereas in the 

 female embryos the tail is only slight^ longer than that of the disk. As the tails in 

 these cases cannot have been mutilated, these proportions are of interest. The localities 

 with the measurements of the embryos are given below. The two younger embryos 

 have the numerous trophonematous filaments still present on all the gill-slits. 



locality and date of 

 collection. 



Length of disk in 

 mm. 



Breadth of disk 

 in mm. 



Length of tail in 

 mm. 



Length of umbilical 

 cord in mm. 



Barkul, 





■ 







Sept. 1914 c? 



60 



60 



105 



U. C. broken, no fila- 

 ments. 



Patsahanipur, 



8-1Ü-14 d 1 



46 



45 



60 



U. C. 15 mm. with a 

 bulbular yolk sac at 

 the end, no filaments. 



Outer Channel, Satpara, 

 2i-iii-i4 9 



33 



30 



40 



U. C. 17 mm. with y. s. 

 at the end, numerous 

 filaments entering gill 

 slits. 



Ditto 9 



27 



24 



30 



U. C. 13 mm. with y . s. at 

 the end, numerous fila- 

 ments entering gill slits. 



The food of this species consists chiefly of Amphipods and other small Crustacea 

 and of burrowing Molluscs such as Solen. 



The alimentary canal is remarkably free from parasites. 

 Distribution : — Bast Indies. 





1775 

 1822 

 1841 

 1878 

 1889 

 1909 

 i9 x 3 



Genus HYPOLOPHUS, Müller and Henle. 

 Hypolophus sephen (Forskâl). 



Raia sephen, Forskâl, Descript. Anim., p. 17, no. 16. 

 Rata sancur, Hamilton- Buchanan, Fish. Gang., pp. 2, 361. 

 Hypolophus sephen, Müller and Henle, Plagiost., p. 170. 

 Trygon sephen, Day, Fish. Ind., p. 740, pi. cxcv, fig. 2. 

 Trygon sephen, Day, Faun. Brit. Ind., Fish., I, p. 50, fig. 21. 

 Hypolophus sephen, Annandale, Mem. Ind. Mus., II, p. 35, pi. v, fig. 1. 

 Dasybatus sephen, Garman, Mem. Mus. Comp. Zool. (Harvard), XXXVI. 



P- 384- 



