12 THE VOYAGE OF H.M.S. CHALLENGER. 



the side of the penultimate joint, which it closely fits ; it terminates in a stout spine 

 like that which bounds the inner edge of the penultimate joint, and its inner edge is 

 furnished with serrate spines similar to those upon the penultimate joint. 



The other thoracic limbs are slender and small in comparison with the first pair, but 

 as only one of them, the third on the right side, was preserved, it is impossible to speak 

 with certainty. That the specimen is a male is also evident from the condition of the 

 abdominal operculum and the second pair of abdominal appendages. 



The operculum or first pair of abdominal appendages is displayed in fig. G of PI. IV. 

 Each appendage consists of an oval plate, flattened but convex ventrally, with a straight 

 inner and a curved outer margin ; the outer margin of each is fringed with a row of 

 simple hairs which gradually increase in length towards the apex of the limb. 



Beneath the operculum are a pair of remarkable appendages, which no doubt Berve 

 the function of a penis ; they are displayed in fig. 7, but as I have only had one 

 specimen of this species at my disposal I am unable to say whether that figure represents 

 the whole of the appendage, or whether any portion has been detached. Each of these 

 appendages consists of a strong basal joint which is shaped somewhat like a joiner's 

 "square;" the nearly straight outer margin is fringed with a number of short simple 

 hairs ; and near to the apex of the limb is given off what apparently corresponds to 

 the endopodite. This consists of two elongated joints which are articulated so as to he 

 almost parallel with each other and with the basipodite ; at the apex of the basipodite 

 are articulated one or two small joints which may represent the exopodite. 



Then follow three pairs of lamellar branchial appendages ; these are covered over and 

 protected by the exopodites of the first pair, which are stout and much calcified ; these are 

 traversed by an oblique suture ; the outer round margin, and to a certain extent also the 

 inner straight margin, are fringed with short simple hairs ; the endopodite of this limb is 

 the first branchial organ. 



The fourth pair of abdominal appendages consists of endopodite and exopodite, the 

 fifth pair of one ramus only ; in every case the shape of these limbs is the same — subtri- 

 angular with a rounded outer and a straight inner margin ; the apex of each is beset 

 with a tuft of long hairs which appear to be plumose. 



The terminal pair of abdominal appendages or uropocla are displayed in fig. 8 of 

 PI. IV. They are biramose, the endopodite and exopodite being subequal in size and 

 beset with numerous longish hairs. 



This species differs from those already described by Haswell and Chilton in the 

 following points : — 



From Stenetrium fractum, Chilton, 1 in the greater length of the fiagellum of the first 



1 Mr. Chilton's description of the species Stenetrium fractum (Trans. New Zealand Soc, veil. xvi. p. 251) is unfor- 

 tunately rather brief owing to the imperfect condition of the specimen examined by him ; hence the points of difference 

 between his species and mine which I have been able to cite are necessarily rather meagre, but I think quite sufficient 

 to discriminate between the two. 



