no Memoirs of the Indian Museum. [Voi.. II, 



chitinous teeth and bearing a bunch of soft, dehcate processes at the tip; one of 

 these processes sometimes longer than the others. 



Mouth parts. — Lahrum bullate, bearing a row of small conical teeth, which 

 increase gradually in size from within outwards ; at the outermost rim of the circle 

 the row is double for about five teeth. Palpi short, conical, bearing long hairs on 

 the dorsal surface. Maxilla with a deep and rather narrow excavation, the inner 

 edge of which bears two or three stout hairs; three very long and stout external 

 bristles, one of which is almost a tooth; the inner bristles short and fine, generally 

 subequal. Mandible with five teeth; its inner arm narrow and elongated. 



In large specimens the length of the capitulum is from 6 to 8 mm. 



Two varieties of this very variable species may be distinguished as follows. 

 Intermediate forms occur, however, although the gradation is slightly abrupt : — 



Var. I (typical form) — 



Carinal margin of the scutum widely separated from the carina, towards 

 which it is concave. Carina laterally narrow. 



Var. II {perfidiosa, nov.) — 



Carinal margin of scutum in contact with the carina for a considerable part 

 of its length, convex towards the carina. Carina much broader laterally 

 than in the typical form. 



I was at first inclined to regard these two forms as distinct species, although they 

 were found together ; but on comparing adult specimens of both I became convinced 

 that they were only varieties. There does not seem to be any constant anatomi- 

 cal difference between them, although both are very variable as regards the cirri, 

 penis, etc. 



Dichelaspis hathynomi has only been found in association with the deep-sea 

 Isopod Bathynomus giganteus, on the pleopods of which it is always, so far as my expe- 

 rience goes, abundant. There are large numbers of Decapod Crustacea in the Museum 

 collections from the same parts of the Bay of Bengal and the Arabian Sea as those 

 in which Bathynomus has been taken, but I have been unable to find on them a single 

 example of D. hathynomi. 



Dichelaspis warwickii (Gray). 



D. warwickii, Darwin, Mon. Cirr., I^ep., p. 120, pi. ii, figs. 6, 6a, 6b; C. W. 



Aurivillius, ''Stud. ii. Cirr.," Kongl. Sv. Vet. Akad. Handl., xxvi, No. 7. 



p. 15, pi. viii, figs, 26, 27. 

 D. equina, Lanchester, Proc. Zool. Soc. Lond., 1902 (ii), p. 385, pl- xxxv, figs. 



7, 7a — d; Annandale, in Herdman's Pearl Oyster Fisheries (Roy. Soc), 



part V, p. 139, fig. 2; Illustr. Zool. '' Investigator ^ Crust. Bnt., pl. v, 



figs. 4—6. 

 CAPITUI.UM irregularly ovoid, the occludent margin being nearly straight and ver- 

 tical, the carinal margin broadly arched ; the apex rounded or bluntly pointed ; the 

 membrane translucent or opaque, often very thick, white or orange- colour, occasionally 



