230 Records of the Indian Museum. [Vol. XVI, 



Anteriorly, owing to the pectoral fins not having grown forwards 

 sufFiciently to meet in the middle, there is a very distinct notch on 

 either side separating the fins from the rounded papilla-like tip of 

 the snout. The disc is only slightly longer than broad and the 

 specimen still possesses the original shark-like form, except that 

 the pectoral fins are better developed though not quite lateral in 

 position even yet. The head at this stage is a prominent struc- 

 ture projecting far above the level of the fins, particularly in 

 the region of the fore- and mid-brain. The eyes are large and 

 prominent, hanging outwards. The spiracles are large, broad and 

 more or less semicircular openings, situated one on either side of the 

 head in a lateral rather than a dorsal situation. The other gill- 

 slits, with the large elongated branchial filaments springing out of 

 them, are situated on the ventral surface, but, owing to the thin 

 and transparent skin, can be seen through it from the dorsal 

 surface. The branchial region is only slightly inflated. The 

 number of gill-filaments is very large. Only a few, however, are 

 shown in the figure for the sake of clearness ; one of these measured 

 over 50 mm. in length. The skin is quite smooth without 

 any tubercles either on the disc or the tail. The pectoral fins 

 show distinct fin-rays. The tail has a rather thin continuous fin- 

 membrane on the dorsal and ventral surfaces ; on the distal half 

 it is better developed on the ventral than on the dorsal side, but 

 there are no fin-rays to be seen. The yolk-sac is rather small and 

 the yolk-stalk has the same structure as has been described in 

 detail for Rh. columnae (p. 229). 



The specimen preserved in spirit is of a white colour except 

 for the pectoral fins, which have a brownish tinge. The yolk-stalk 

 is of the same colour as the embryo but the yolk-sac is yellowish. 

 Ventrally the embryo appears brownish owing to the colon shining 

 through it. 



Measurements of the female specimen : — 



Ivcngth of the disc . . 29-1 mm. 



Maximum breadth of the disc . . 26 mm. 



Interorbital distance . . 55 mm. 



vSnout (measured from the 



mouth) . . • • 5*3 inm. 



Mouth to vent 

 Tail . . 

 Yolk-sac 

 Yolk-stalk 



23*4 mm. 

 38*2 mm. 



10 mm. by 7 mm. 



i6'5 mm. 



Internal anatomy. — The colon is the largest of all the parts 

 of the alimentary canal and lies on the right side; it has the 

 yolk-stalk opening directly into it on the dorsal side, there being 

 no internal yolk-sac. In embryos of T. hleek&ri the duct, according 

 to Alcock/ opens ventrally, but in the specimens of this species 

 and of T. uarnak dissected by us it opens dorsally. The duode- 



Mag. Xut. Hist. (6), IX. p. 425 (189; 



