igio.] N. ANNANDAI.B and J. T. Jenkins : Plectognathi and Pediculati. 9 



Of the 61 species in the above hst, only 17 have been taken by the "Golden 

 Crown," although 34 of the 54 Batoidei known from Indian seas were obtained. 

 This is evidently due to the fact that the great majority of the Plectognathi are reef- 

 haunting species not found in water suitable for the operations of a trawler. Three 

 species in the list {Triacanthodes ethiops, Halimochirurgus centriscoides and Ostracion 

 fornasini) have been added to the Indian fauna by Col. Alcock/ while five have 

 recently been recorded from the south-western limits of the Indian seas by 

 Mr. Tate Regan in his account of the fish taken off the Maldives and in other parts 

 of the Indian Ocean by Prof. Stanley Gardiner.^ These five species, only the first of 

 which is represented in the collection of the Indian Museum, are Monacanthus oculatus, 

 M. nematophorus , Aluteres nasicornis, Tropidichthys valentim and T. hennettii. Two 

 additional species have recently been taken by the R.I. M.S. "Investigator" in 

 fairly deep water, both new to the fauna, namely, Tetrodon spinosissimus and Tropid- 

 ichthys investigatoris, sp. nov. The former was described by Mr. Tate Regan from the 

 Saya de Malha Bank in the Indian Ocean, and is represented in the Indian Museum by 

 several specimens from the Gulf of Martaban and from Hongkong. Two species of Tri- 

 acanthus and one of Diodon, not recognized by Day, have been taken by the "Golden 

 Crown." Most of the forms dealt with in this paper are, however, well known ; only 

 two new species are described here {Tropidichthys investigatoris a.nà Halieutaea indica), 

 while a third (Triacanthus weheri) has recently been described by Mr. B. I^. Chaudhuri. 



The families and genera of the Plectognathi have so often been discussed that in 

 most cases it will be unnecessary for us to describe their peculiarities, which are fully 

 described in Giinther's Catalogue of the Fishes in the British Museum, vol. viii. 



Sclerodcrmi. 



Key to the Families and Indian Genera of Sclerodermi. 



Family I, Triacanthidae. 



Skin covered with small scales; body compressed; a spinous dorsal fin consisting 

 of at least two spines ; a pair of stout moveable ventral spines. 



A. — Snout moderately produced; teeth small, conical, 



in a double series . . . . . . Triacanthodes. 



B. — Snout moderately produced; teeth of the outer 



series incisor-like . . . . . . Triacanthus. 



C. -Snout produced into a long, curved, perfectly 



tubular organ . . . . . . Halimochirurgus. 



1 Journ. Asiat. Soc. Bengal (ii), vol. Ixiii, p. 137, pi. vii, fig. 6 (1894), and vol. Ixv, p. 338 (1896) ; 

 Proc. Asiat. Soc. Bengal, 1899, p. 78; Illusty. Zool. R.I.M.S. '' Investigator ^ Fishes, pi. xv, fig. 9, and 

 pi. xxxi, fig. 3. 



'^ Gardiner's Fauna and Geogr. Maldive and Laccadive Arch., vol. i, p. 279, and Trans. Linn. Sac. 

 London (2), xii, p. 252. 



