226 MR. A. ALCOCK ON A VIVIPAROUS [Apr. 7, 



This completes the subfamilies and recognizable genera of Slugs. 

 I have in this paper preferred to give the facts almost without any 

 discussion of the problems illustrated by them, partly because such 

 a discussion would be more suitable in connexion with a paper of 

 less limited scope, and partly because it would render the present 

 contribution unduly long. 



2. On a Viviparous Bathybial Fish from the Bay of Bengal. 

 By A. AlcocKj M.B.^ Surgeon I.M.S. (Communi- 

 cated by Prof. J. Wood-Mason, P.Z.S.) 



[Eeceived March 16, 1891.] 



In the 'Annals and Magazine of Natural History' for November 

 1889 (vol. iv. ser. 6, pp. 389-390), I described under the name of 

 Saccogaster maculata a new type of Brotuline Ophidiids allied to 

 Catcdax. The two specimens upon which the genus was established 

 were described as females 3g and 4 inches long, with gravid 

 ovaries ; they were taken in 193 fathoms off the mouths of the 

 Gangetic Delta. 



Among the characters which distinguish Saccogaster the two 

 most marked are its sac-like abdomen and its loose imperfectly- 

 scaled skin. 



On the 24th D^ember last, in a very successful haul of the trawl 

 in 240 fathoms off the mouths of the Kistiia Delta, another speci- 

 men of Saccogaster maculata was obtained. It proved to be an 

 adult male, 3| inches long, with ripe milt. Though otherwise 

 resembling the female in external characters, it differs in having a 

 deep post-anal depression or excavation, which is filled by a large 

 bilobed papilla with the genital pore opening into the groove between 

 the lobes. The papilla is thick, fleshy, and smooth ; each lobe is 

 about 2 mm. long and r25 mm. broad, and is pigmented at the 

 apex. 



In consequence of the discovery of this genital papilla a micro- 

 scopic examination of a portion of one of the ovaries of the original 

 type specimen was made, and it was found that in the ova as 

 they lie in situ the development of the embryo is already far 

 advanced. 



Unfortunately the material is not in the best state of preservation, 

 but the ova are still in a sufficiently good condition to show the 

 general relations of the embryo. 



The embryos are vermiform ; they are about 1*5 mm. in length, 

 and are closely applied to the yolk-sac, which they embrace through 

 rather more than three-quarters of its circumference ; the cerebral 

 lobes, optic vesicles, and long free tail-fold are plainly apparent, but 

 beyond these and the continuous bright line of the notochord 

 nothing can now be made out ; the yolk-sac is a little more than 



