32 



Memoirs of the Indian Mtiseum. 



[Vol. II, 



147-5 cm. 



102-5 cm 



17875 „ 



136-25 ,, 



197-5 ,, 



220-83 ,, 



37-5 ,, 



25-0 ,, 



26-5 „ 



21-25 „ 



16-25 ,, 



15-0 ,, 



96-25 







Ganjam in about 24 fathoms. Although they do not agree in every respect with 

 Blyth's description of the species I think these specimens must belong to it. Blyth's 

 specimens appear to have perished and there are no others, except the ones des- 

 cribed, in the Indian Museum, or, indeed, so far as I can discover, in any other collec- 

 tion. The measurements of my specimens were as follows : — 



2 cf 



Ivcngth of disk 



Breadth of disk 



Length of tail 



Length of snout from eyes 



Distance between eyes 



Nasal flap . . 



Mouth to vent 



Trygon imhricata (Bloch and Schneider). 



T. imbricata, Müller and Henle, op. cit., p. 164 ; Day, op. cit., p. 52. 

 T. walga, Müller and Henle, op. cit., p. 159, pi. 51 ; Day, op. cit., p. 55. 



Size small (adults 210 — 220 mm. across the disk, young 90 — 100 mm.). 



Disk about as long as broad in the adult, broader in the young, always with the pec- 

 toral fins broadly rounded ; the snout not greatly produced, occupying about one- 

 third of the disk, forming an angle which is nearly a right angle ; its length from 

 the eyes about 2|- times the distance between the eyes. Eyes nearly as large as 

 spiracles, not very prominent. 



Tail variable in length, sometimes barely as long as the disk, sometimes twice as 

 long or even longer, proportionately longer in the young than in the adult. On 

 either side there is always a thick but low ridge, while along the mid-dorsal line a 

 narrow groove can generally be detected. Sometimes this groove contains a low 

 fold, which is much lower than the tail and is more strongly marked on the distal 

 half of the tail than it is on the basal, although it does not reach the tip. More 

 rarely there is a corresponding fold on the ventral surface, but even when both are 

 present they are low and inconspicuous. As a rule there are two narrow serrated 

 spines on the tail. 



Colour. — Ventral surface white. Dorsal surface of brownish clay-colour, occasionally 

 with obscure darker spots and usually becoming paler on the edge of the fins. The 

 lateral ridges on the tail white. 



Skin. — The lepidosis is as Variable as are the proportions of the tail, but the two charac- 

 ters are not correlated. In many adult individuals the back and head (but not the 

 pectoral fins) are covered with small flattened denticles which do not differ from one 

 another markedly as regards size or shape. There are sometimes, however, several 

 enlarged tubercles on the midline of the scapular region, while often a row of den- 

 ticles bearing backwardly directed spines can be detected in the middle Hue at the 

 posterior end of the disk and on the base of the tail. They vary in size and develop- 

 ment. Sometimes, even in adults, the disk is almost naked. 



