582 MRS. E. W. SEXTON ON THE 



truncate. The long spine on the hind margin in Chevreux's 

 figure, (16) pi. xi. fig. 2 a, is the longest of a group of 3 inset 

 on the under side of the hand, and projecting beyond the hind 

 margin. The palmar mai-gin is mentioned by Chevreux (p. 91) 

 as affording a distinguishing character for the two forms — concave 

 for pectinat'us, and convex for dellavcdlei, — but an examination of 

 a series of specimens shows conclusively that this diflerence is due 

 to sex. In the male (figs. 15 & 18) the margin is concave, and 

 the palmar angle forms a right angle with the hind margin ; 

 in the female (fig. 17) the palmar aiigle is rounded, the 

 curve commencing at the insertion of the finger, and merging 

 imperceptibly into the hind margin. The palm is strongly 

 serrated in all ; in the female the serrations turn the corner and 

 reach as far as the large spine just referred to. The pali^ar spines 

 are of the same structure as those of the type species. The finger 

 is more than twice the length of the palm (a little longer in pro- 

 portion in the young form), curved, with a strong auxiliary claw ; 

 a long, stifi', finely serrated spine and 1 setule are inset in the 

 notch, 1-2 setules behind the claw ; the rest of the inner margin 

 is firmly serrated. 



Second Gnathopod (figs. 19 & 20) as described by Grube, 

 Norman, and Delia Valle. Figures of the finger, so characteristic 

 of the species, are given from Norman's and Chevreux's specimens 

 in order to show the identity of the two forms pectinatus and 

 dellavallei. Grube's specimens agree exactly with these. In the 

 young form the finger is slightly longer in proportion to the pre- 

 ceding joint than in the older animals, not equalling quite half 

 its length in Norman's specimens, and only about one- third the 

 length in Grube's largest. 



Perceopods 1 and 2 glandular, alike in structure ; 2nd joint large, 

 fringed posteiiorly with long delicate sette, more numerous on the 

 2nd peraeopod ; anterior margins with from 4-6 similar setse : 

 4th joint about half the length of the 2nd, slightly expanded 

 distally ; 5th joint narrower and shortei- than 4th ; 6th joint 

 slightly longer than the 4th ; the two terminal joints tapering 

 gradually to the acute tip of tlie 7th ; the 7th subequal to the 6th 

 in length, with the glandular aperture opening at the tip. 



Hinder Perceopods (fig. 21) more strongly built than the pre- 

 ceding ; rapidly increasing in length. Perjeopod 3 : 2nd joint 

 large, a little longer- than broad, equalling in length tlie 3 fol- 

 lowing joints taken together ; both margins convex, the anterior 

 beset at intervals with 7 small sensoiy spines, the first 3 un- 

 accompanied by setie, the 4th with 1 seta, the 5th with 2, 6th 

 with 3, and the distal one with 4 ; posterior margin produced 

 below in a rounded lobe, crenulate, 6 of the crenulations with 

 setules inset, the 2 crenulations on the lobe each with a ciliated 

 hair ; 3rd joint short and bi'oad, with a cluster of setaj, 1 ciliated 

 hair, and 1 spine ; 4th joint half the length of the 2nd, stout, 

 slightly expanded anteriorly, with the spines of the structure 

 peculiar to the hinder perseopods and uropods (fig. 21); 5th joint 



