1860.] The Cartilaginous Mshes of Lower Bengal. 43 



appearance — and the tail is wholly naked. In another, 15 in. (to 

 base of tail), the medial portion of the back is densely tuberculated, 

 and a series of tubercles (about six in number across) is continued 

 along the base of tail to its spine ; in another, \9\ in. (to base of 

 tail), with tail 6 ft. in length, the series of caudal tubercles is still 

 scarcely wider proportionally, and the tuberculated portion of the 

 back is comparatively much narrovver than in the several preceding 

 species, being little more than a fifth of the entire breadth — instead 

 of fully a third as in Tr. Bleekeri of half the size. In the adults, 3 ft. 

 across, — a fresh one before me is 2f . ft., and 2^ ft. to base of tail, 

 with tail 7| ft., — the tubercles of the dorsal surface remain as 

 in the last described, and cover just the upper half of the base of the 

 tail as far as the spine, the lower half being quite naked. In general, 

 there are a few tubercles rather larger than the rest, forming an 

 irregular mesial line from the anterior third of the dorsal surface to 

 the caudal spine. Half-grown individuáis have commonly two larger 

 tubercles on centre of back, either both heart-shaped or the anterior 

 globular, while larger specimens shew an intermediate tubercle ; and 

 up to a considerable size, the thong of the tail is more sparsely tuber- 

 culated than in the others. In this particular species, also, the 

 curious teeth are distinctly of a larger size than in the others, when 

 examples of the same size are compared together. 



22. Tr. yariegatits, McClelland, Cale. Journ. Nat. Hist. I, 60, 

 and pl. II, fig. 2. Shaped as in the last, and remarkable — even when 

 half grown — for the caudal tubercles completely surrounding the tail 

 to very near its base, — whereas in Tr. Russellii they never more 

 than half surround it as far as the spine, even in the largest indi- 

 viduáis. In an example of yariegatus, measuring 16 in. to base 

 of tail, with tail exceeding 3| ft., the tubercles already nearly surround 

 it anterior to its spine. Moreover, in examples of equal size, the teeth 

 of Russellii are conspicuously larger. The markings, too, are quite 

 different ; Tr. yariegatus having the dorsal surface uniformly and 

 beautifully marked throughout with meandering lines, the dark and 

 palé colour in equal proportions or even the dark predominating — 

 not as represented in McClelland's figure. Length of one 3 ft. to 

 base of tail, and 3 ft. 4 in. in greatest width : tail not quite perlect, 

 but of the same proportionate length as in the others. The bands 



g 2 



