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



Observations. — In general, the shape of this Pycnogomcl resembles that of PhoxicMU- 

 dium digitatum, Bohm. However, in many respects, it may be easily distinguished from 

 this and other species of PhoxichiUdium hitherto described ; for instance, hj the presence 

 of ovigerous legs in the female, by the presence of auxiliary claws, by the number of 

 joints (10) of the ovigerous legs, &c. Like most other species of the same genus, this 

 species seems only to occur in shallow water (depth 45 to 175 fathoms) not far from the 

 coast. 



Phoxichilidiuin patagonicum, var. elegans, n. var. (PL XII. fig. 10). 

 Diagnosis. — Like PhoxichiUdium jycitagonicum, Hoek, only much more slender. 

 Description. — 



Length of the proboscis, 



Total length of the body, . 



Length of the abdomen, 



Length of the leg of the third pair, . 



Length of the ovigerous leg, 



A young specimen has the different thoracic segments by no means so concentrated 

 or robust as is the case in the specimens of PhoxichiUdium patagonicum ; the lateral 

 processes are much more widely separated ; in general the length of the body, in com- 

 parison with that of the legs and of the proboscis, is much more considerable. The oculi- 

 ferous tubercle is furnished with four eyes, but the two foremost are much larger than 

 the two others. The length of their legs and their joints is not very different from that of 

 PhoxichiUdium patagonicum ; the only difference being that the total length is compara- 

 tively less. The claws and the auxiliary claws are as in PhoxichiUdium patagonicum. 

 About the sex of this specimen I do not feel Cjuite sure : most probably it is a young female. 



Habitat.— Citation 320. February 17, 1876. Lat. 37° 17' S., long. 53° 52' W. 

 Depth of the sea, 600 fathoms. Bottom temperature, 27° C. Bottom of the sea, hard 

 ground. 



Observations. — The single specimen of this form resembles PhoxichiUdium j^cita- 

 gonicum so strongly that I hesitated long whether or not I should consider it as 

 specifically distinct. My study of other species, younger and older specimens, has 

 convinced me that, as a rule, as the animal advances in age, its slenderness increases. 

 Now, in the present case, a young specimen shows considerable slenderness, while 

 the full-grown female is much more concentrated. That it is a young sj)ecimen is proved 

 by the rudimentary condition of the ovigerous leg. I therefore feel inclined to consider 

 this form as a variety of my PhoxicJiiUdium patagonicum. Considering the difference 

 in depth of the stations at which that species and the present form were dredged, we 

 have here most probablj'- an instance of the influence of surrounding circumstances on the 

 form of an animal. 



