174 J. Wood-Mason — On Rhopalorhynchcs Kroyeri. [No. 8, 



and nearly as long as, but slightly stouter than, the filiform proximal moiety 

 of the rostrum ; and are suddenly expanded at their articular ends, each somite 

 presenting the appearance of a cylinder with a greatly truncated cone affixed 

 by its truncated surface to each end. The fourth and last somite is scarce 

 half the length of those that precede it, and is similarly expanded at its 

 anterior end only. From the sides of the expansions at the posterior 

 extremity of the 2nd and 3rd spring two somewhat inflated outwardly- 

 directed, obconic processes which might, at first sight, be mistaken for the 

 first of the basal joints of the legs from their close similarity to these, but 

 which are in reality one with the somite from which they arise : precisely 

 similar processes carry the legs both of the first and of the last somite in 

 which, however, they diverge like the arms of the letter Y. Wedged in 

 between the roots of these processes of the last somite and the posterior 

 boundary of its ventral arc, lies a minute, obtusely -conical tubercle with a 

 large circular (anal) aperture at its extremity. This is the abdomen, a very 

 evident, though rudimentary, structure in most Pycnogonida and even 

 biarticulate in one species (in Zetes hispidus, Kroyer),but here so reduced in 

 size as to be quite invisible from above, and only demonstrable with difficulty 

 from below whence it appears, in ordinary positions, under the microscope as 

 a convex, ovoidal or heart-shaped plate. It, moreover, looks downwards and 

 slightly backwards, instead of upwards and backwards or directly backwards 

 as it usually does. 



The legs are long, slender, simple, equal in length, rather more than twice 

 as long as the body including the rostrum, and are composed of eight joints, 

 terminated by a weak, slightly curved claw. Their three basal joints are as 

 broad as long, equal, and almost globular ; the fourth is club-shaped at the 

 distal end ; the fifth is all but as long as the fourth and, with the remaining 

 joints, perfectly filiform ; the sixth is shorter and about twice the length 

 of the two last together ; these are subequal. 



Length of the body including the rostrum, 13 mm. 



„ „ legs, 26 mm. 



„ „ 2nd pair of cephalic appendages, 10 mm. 



„ 3rd „ „ „ „ 12 mm. 



From the linear from of the body and the slenderness of the legs, I 

 conclude that my specimen is a male, a conclusion by no means invali- 

 dated by the presence of the third pair of cephalic appendages, which, being 

 apparently invariably developed in both sexes throughout several genera, 

 {Nymphon^ etc.) consequently possesses no value in the determination of ques- 

 tions of sex. 



Jlab. — Dredged by the writer at Port Blair, Andaman Islands, in 25 

 fathoms of water, at which depth the bottom was clothed mth a dense 



