99 



Except in point of size, the species of Diplacanthopoma hardly differ from 

 one another. 



77. Diplacanthopoma Rivers- Antler soni, Alcock. 



Diplacanthopoma Rivers- Andersoni, Alcock, Ann. Mag. Nat. Hist. Ang. 1895, p. 144: Illustrations of the 

 Zoology of the Investigator, Fishes, pl. XVII. fig. 1. 



Bight branchiostegals. 



Head about a fourth the total length : greatest height of the body, at the 

 shoulder, equal to the length of the head without the snout. 



Snout depressed, on a very much lower plane than the occiput, its length as 

 much exceeds that of the eye as it falls short of the width of the interorbital 

 space. Nostrils large : one immediately in front of the eye, the other near the 

 edge of the snout. 



Major diameter of the eye between a sixth and a seventh the length of the 

 head. 



Upper jaw half as long as the head, overlapping the lower jaw. Jaw-teeth 

 in broadish bands, palatine and vomerine teeth in narrowish bands. 



The spines of the operculum project freely. Only three enlarged gill- 

 rakers on the outer side of the first arch, and those entirely in the upper half of 

 the arch. 



The bases of the dorsal and anal fins are invested in a thick scaleless 

 glandular skin similar to that of the head. The anal begins a head length 

 behind the axilla. Pectorals and ventrals of no great length. 



Each ventral fin consists of a single stout fluted filament, looking like two 

 or more rays intimately fused together. 



Colours in spirit : body purplish brown ; head and fins much darker. 



A single specimen from off the Indus Delta: length a little over 15 inches. 



The specimen is a pregnant female : the ovaries open on a fleshy cushion, 

 behind the vent. 



Regd. No. 14136. 



The ovaries consist of a densely packed mass of embryos and ova enclosed 

 in a thin but extremely tough capsule. The capsule is abundantly supplied with 

 blood by the ramifications of a large branch of the mesenteric artery. 



There is no attachment or adhesion of any kind between the ovarian capsule 

 and its contents. 



The embryos form a thick surface layer immediately beneath the capsule, 

 enclosing a central mass of largish (a little over 1 millim. diameter) ova, which 

 consist entirely of yolk-spherules, without any trace of an embryo or even of a 

 germinal area. 



