120 

 70. Aegeon medium (Alcock & Anderson). 



Pontocaris media, Alcock and Anderson, Ann. Mag. Nat. Hist., April 1899, p. 282. 

 Illustrations of the Zoology of the Investigator, Crustacea, Pl. XLI. Pig. 6. 



Differs from Aegeon affine only in the following characters : — 



(1) the rostrum reaches nearly to the end of the eyestalks, is dorsally 

 grooved and is not cleft at tip, and has a larger spine on either side of its base : 



(2) the supra-marginal carina on either side of the carapace is coarsely 

 serrulate, or beaded : 



(3) the first 5 abdominal pleura, though produced in a vertical direction, 

 have blunt or truncated tips : 



(4) the 2nd thoracic legs are of the same length in both sexes, not reaching 

 far beyond the carpal articulation of the hand of the 1st pair : 



(5) the last 3 thoracic sterna are more distinctly carinated in the female ; 

 but in the male they are not sharper than in Ae. affine. 



As in Ae. affine the outer antennular flagellum, in the male only, is foliace- 

 ous up to a terminal filament. 



The carapace in an adult female is 12 millim. long, in an adult male 9 

 millim. The abdomen in an adult female is 30 millim. long, in an adult male 

 22 millim. 



From the Andaman Sea 55 and 60 fathoms. 



The species is perhaps identical with Pontocaris propensalata, Bate. 



Regd. Nos. — jg— (Types of the species) : — . 



Subgenus Parapontocaris, nov. 



Closely related to Aegeon, as restricted by Stebbing, from which it differs 

 only in the following particulars : — 



The integument, though extremely dense and hard, is not thick and coarse ; 



The abdominal pleura are produced antero-posteriorly and are rounded, 

 instead of being produced in a vertical direction : the abdominal sterna are 

 without a strong median spine. 



The eyes are larger and blacker. The antennal scale is much longer than 

 broad. The exopodite of the 1st pair of thoracic legs is larger. 



The branchial formula is, however, exactly the same as that of Aegeon 

 cataphractus, there being two branchias (one large, the other small and a good 

 deal concealed) to the somite that carries the external maxillipeds. 



