PYCNOGONIDA. 5 



A projection beyond the insertion of the terminal claw, which occurs in some 

 species, is called the Heel, a term introduced by Mr. L. J. Cole. Two other expressions 

 have been adopted for purposes of convenience. In very many species, not to say 

 genera, there occurs a thickening of the skin on the sides of the legs, not infrequently 

 also on some of the other appendages ; this takes the form of a narrow and conspicuous 

 line, usually of a reddish colour, and so it has been termed the " lateral line." The 

 other feature concerns the setae. At the extremity of most of the joints there is 

 a fringe of more or less specialised setse, sometimes surrounding the joint, but 

 frequently more conspicuous on the dorsal or the ventral aspect. This has been termed 

 the distal fringe, a name which does not appear to be inappropriate. 



Precise measurements are invariably necessary with regard to the legs. One 

 leg is generally considered to be sufficient for this purpose, and as Dr. P. P. C. Hoek 

 adopted the third leg of the right side for this purpose wherever possible, the same 

 limb has been used here. 



PHOXICHILUS. 



This genus is readily distinguished by its slender form and the complete absence 

 of chelifori and palps. The ovigers too only occur in the male, and are seven-jointed. 

 Among other characters may be mentioned the presence of a " collar " between the 

 cephalon and the proboscis. This, however, is deficient in the species described below. 



Numerous species have been assigned to this genus, but the difficulties of species 



discrimination is increased by the absence of two of the normal number of appendages, 



and necessitates some modification of the generic characters. No less than six species have 



been described from European seas, but their specific distinctness is open to question. 



Three others have been found in distant seas, and a fourth now described is from the 



extreme south. 



Phoxichilus australis. 



(Plate I., fig. 1.) 

 Specific characters : — 



Body slender, with lateral processes very widely separated and with the long legs completely 

 covered with very minute stiff setse. 



Tarsus with a very prominent ventral spine, and three to five proximally on the propodus, 

 which projects distinctly beyond the insertion of the terminal claw and auxiliaries. 

 No distinct collar anteriorly to cephalon. 



Body slender, with the lateral processes long and very widely separated ; perfectly 

 smooth to unassisted vision, but with a 1-in. objective extremely minute spines can be 

 detected ; segmentation very prominent and immediately behind each pair of lateral 

 processes. 



The Cephalon is small, but stouter than the trunk, truncated anteriorly with the 

 angles bevelled off. No collar exists as such, but a band of thin chitinous skin, 

 characteristic of an articulation, occurs between the cephalon and the base of the 

 proboscis. 



