30 



Memoirs of the Indian Museum. 



[Vol. II, 



This species appears to resemble T. akajei in several respects but to differ in size, 

 in the proportions of the disk and tail, lepidosis and character of the teeth and 

 jaws. Possibly it may be identical with Bleeker's Trygon dadong, but on the whole I 

 think this improbable. 



Two adult males were taken by the ' ' Golden Crown ' ' off the Ganjam coast in 

 23 to 27 fathoms in March, 1909. The type (dried skin, mouth in spirit) is numbered 

 F âA^â in the Museum registers. 



To facilitate comparison I give the measurements of specimens of the six allied 

 species, Trygon uarnak, Trygon gerrardii, Trygon favus, Trygon bleekeri, Trygon alcockii 

 and Trygon jenkinsii together. The specimen indicated with a * was measured in spirit. 



Name of species. 



Sex. 



Length 



of 



disk. 



Width 



of 

 disk. 



lyength 

 of 

 tail. 



Nasal 

 flap. 



Distance 



between 



eyes. 



Snout. 



Trygon uarnak 



c? 



122-5 cm. 



150-0 cm. 



321-25 cm. 



12-75 cm. 



25-0 cm. 



37-5 cm. 





9 



120-0 ,, 



1525 ,, 



43875 „ 



15-0 „ 



2375 =. 



32-5 , 



„ 



2 (juv.) 



2375 „ 



40-0 ,, 



80-0 ,, 



2-5 „ 



6-25 „ 





„ 



* Ç (em- 

 bryo). 



23-5 ,. 



20-5 „ 



67-8 „ 



2-9 ,= 



4-5 » 



67 , 



Trygon gerrardii 



9 



55-0 „ 



67-5 „ 



150-0 



5-62 „ 



lo-o 



15-0 „ 



Trygon favus (type) . . 



5 



iiS'o ,, 



130*0 ,, 



207-5 „ 





30-0 ,, 



36-25 ,, 



Trygon bleekeri 



9 



118-75 „ 



117-5 „ 



202-5 



875 ., 



15-0 ,, 



32-5 >. 



„ 



9 (juv.) 



41-25 „ 



46-25 ,, 



13875 „ 



5-0 „ 



7-5 >, 



15-0 ,, 



Trygon alcockii (type) . . 



5 



73-0 „ 



85-0 ,, 



102-5 



7"0 .. 



ii-o 



i6-5 „ 



Trygon jenkinsii 



c? 



7875 >, 



10375 M 



iio-o 



875 „ 



16-25 ,, 



22-5 ,, 



,, (type).. 



<? 



8o-o ,, 



10375 >, 



II2-5 „ 



7-5 » 



15-0 ,, 



20-0 ,, 



Trygon marginatus, Blyth. (PI. iii, fig. 2.) 



T. marginatus, Blyth, Journ. Asiat. Soc. Bengal, xxix, p. 38 (1861) ; Day, Faun. 

 Brit. Ind., Fishes, p. 54. 

 Disk broader than long, with the pectoral angles somewhat narrowly rounded. The 



snout rounded as a whole, but sometimes with a short terminal projection ; length 



of snout 3|- to 4^ times in length of disk. Eyes small. 

 Tail much longer than disk, without caudal folds. There is only one large serrated spine. 

 Colour. — Dorsal surface grey, with a distinct blackish tint and without any tinge of 



brown. In the male a series of livid bluish marks of an irregularly crescentic 



outline runs round the disk at some little distance from the margin. Ventral 



surface white with a broad blackish margin laterally and posteriorly ; this 



margin sometimes indistinct. Tail blackish. 



