A NEW COPEPOD FROM A MARSH CRAB — HUMES 385 



tinctly demarcated, sixth about as long as the first, this and the last 

 two podomeres gradually tapering in size; distal end of the eighth 

 bearing a minute chnv; ventral sides of podomeres 1 to 6 setose, 

 a pectinate seta on 4 and 6, and an athetask similar to that in the 

 female on the distal ventral angle of the fourth podomere; a few 

 setae dorsally and terminally on the eighth podomere. 



Second antennae, mouth parts, and first four pairs of legs all like 

 those of the female. Fifth leg (fig. 18, g) very much smaller than in 

 the female, reduced to a low lamellar process bearing two pectinate 

 setae medially, then a long pedicel terminating in two setae of which 

 the inner one is the longer, and outermost a seta set upon a single- 

 jointed pedicel. 



In about half of the male specimens a single yellowish-brown 

 spermatophore (fig. 18, /) was seen, usually in the genital segment 

 (sixth thoracic). 



Measurements of 10 males: Total length, exclusive of setae, 0.583 

 mm. (0.545-0.621 mm.) ; greatest width (first thoracic segment), 0.219 

 mm. (0.104-0.147 mm.) ; length of anal setae, 0.470 mm. (0.400-0.524 

 mm.). 



Color like that of the female. 



Remarks. — This species differs significantly from the two pre- 

 viously known species of Caiicrincola in the following respects: 



(1) Anterior antennae in the male with eight podomeres; wilsoni 

 has only three podomeres. 



(2) Fifth leg of male with five terminal setae; in jamaicensis 

 there are two and in wilsoni four. 



(3) Fifth leg of female with six setae on the proximal podomere 

 and five on the distal podomere; in jamaicensis there are six on the 

 proximal and six on the distal podomeres, and in tailsoni seven on 

 the proximal and two on the distal podomeres. 



There are many other minor differences in setal arrangements and 

 in the mouth parts that may be used to separate G. pluniipes from the 

 other two species. C. plumipes appears to be more closely related 

 to the Jamaican species than to the Japanese form. The number of 

 minute setae on the body and appendages was found to vary slightly 

 in different individuals of the same sex, and hence the numbers given 

 above should not be regarded as absolute. 



Members of this genus have been found in the gill chambers of 

 both terrestrial and aquatic crabs. They show little modification 

 for a parasitic way of life and have retained the ability to swim 

 freely. The life cycles of these species, though unknown at present, 

 are probably intimately connected with the molting of the crabs and 

 their migrations into the sea for food getting or for development 

 and hatching of their eggs. 



