igio.] N. Annandale and J. T. Jenkins . Plectognathi and Pediculati. 13 



An abnormal specimen in the collection, while agreeing in other respects with 

 typical examples, shows no trace of the dorsal spine. 



Aluteres scriphis (Osbeck). 



Monacanthus scriptus, Day, op. cit., p. 483, 



At least one specimen was taken by the "Golden Crown ' ' on the same gromids 

 as the last species. 



Family OSTRACIONTIDAE. 



Genus Ostracion, Artedi. 



The only species of this genus taken by the "Golden Crown ' ' are O. gibbosiis (the 

 0. turritiis of Day's books) and 0. nasus. The two species do not appear to have 

 quite the same distribution in the Bay of Bengal, for while 0. nasus has been taken 

 in considerable numbers in the muddy waters opposite the mouths of the Ganges, 

 0. gibbosiis appears to be characteristic rather of the 5//?^«rtr/« grounds off the Madras 

 coast and the rocky bottom off Arakan. Both species occur, however, in the 

 Andamans. 



Alcock (Journ. Asiat. Sac. Bengal (ii), vol. Ixv, p. 338) has added 0. /oi'nasini,a 

 species widely distributed in the Indian Ocean, to the fauna of British India; but we 

 have been unable to find his specimen, which was taken off Ceylon in 34 fathoms, in 

 the collection of the Indian Museum. The species is easily distinguished from its ally 

 T. cornutus by its much shorter superciliary spines, which are parallel or slightly con- 

 vergent, and by the fact that it possesses a large, conical, compressed spine in the 

 middle of the back. 



Gymnodontes. 



The families here recognized are clearly distinguished by Day as "groups," 

 except that he does not separate the Diodontidae, which have only a single tooth in 

 each jaw, from the Tetrodontida;, which have two. 



Family TETRODONTIDAE. 



Considerable difference of opinion exists among ichthyologists as to the number 

 of genera that should be recognized in this family. We are able to distinguish three 

 among the Indian forms , as follows : - 



A. — Back rounded or flat ; nostrils conspicuous. 



{a) Dorsal and anal fins with more than 20 rays 



each .. .. .. •.. Xenopterus. 



(a') Dorsal and anal fins with not more than i5 rays 



each . . . . . . . . Tet radon . 



B. — -Back compressed into a ridge ; nostrils very inconspicuous. 

 Dorsal and anal fins with not more than lO ra3's 



each . . . . . . . . Tropidichthys. 



