176 " THETIS " SCIENTIFIC RESULTS. 



Abdomen longer than the carapace ; somites very distinct ; the 

 last two segments have their dorsal walls well calcified. 



The first segment of the abdomen bears a pair of slender genital 

 appendages ; they are slightly compressed, acute at their apices, 

 and measure about 3 mm. in length. The second, third, fourth 

 and fifth abdominal appendages of the left side biramous ; the 

 branch on the fifth is very short, measuring about 2 mm. in 

 length ; sixth pair of appendages very unequal, the left one being 

 much the larger. Telson slightly unequal, with a smooth rounded 

 margin. 



The male has a pair of genital appendages on the first abdo- 

 minal segment ; they are equal in length to those occurring in the 

 female, but differ in shape towards their extremities, and are 

 lancet-like and longitudinally- channelled. 



The second segment has a pair of subequal uniramous append- 

 ages ; the three following segments have each a single biramous 

 appendage on the left side. 



General colour pale cream ; eye peduncles light brown ; cornea 

 blackish-brown ; proximal portion of the cai'pal joints of the first 

 three pairs of legs with a narrow, transverse, bright red band ; 

 each band is more or less interrupted on the lower surface. 



Chelipedes of a reddish tint, the colour fading to cream towards 

 the extremities. 



Proximal lamellae of the gills oblong ; inner apical margin 

 evenly curved and trending outwards ; outer border with a slight 

 angular sinus, situated at about one diameter from the summit. 

 As the distal end of the gill plume is approached the sinus 

 gradually diminishes in size, and the outer apical border becomes 

 obliquely truncated ; the last series of distal plumes — about 

 twelve rapidly diminishing pairs — are simple rounded filaments. 



This species is very closely allied to Sympagurus arcuatus, 

 Edwards and Bouvier,* from which it differs in its larger size, in 

 the shape of the gill lamellae, in the granulation and shape of the 

 larger hand, which is more transversely truncated at the extremity, 

 and finally in having a small spine at the anterior end of the 

 ocular segment, after the manner of Diogenes, hence the specific 

 name. 



Length of body from rostrum to tip of telson 70 mm. 



„ ,, carapace ... ... ... ... 17 ,, 



Width of front 8 



Length of right ocular peduncle ... ... /) ,, 



Diameter ,, ,, ,, at base ... 18 ,, 



Mem. Mu8. Comp, Zool., xiv., 3, 1893, p. 67, pi. v., figs. 21-28. 



