DOEOPYGUS. 137 



lamina" (/ m) four setae, all of them being, as usual, 

 finely and densely plumose, and doubtless branchial in 

 function. The first foot-jaw (fig. 6) does not differ 

 materially from that of D. pulex ; the second (fig. 7) is 

 small, subovate, and fringed with about ten plumose 

 hairs. Branches of the first pair of feet (fig. 8) 

 nearly equal ; marginal spines of the external branch 

 long and slender ; branches of the second and third 

 pairs (fig. 9) subequal, the external branch bearing 

 setae in place of spines, the internal branch 2 -jointed ; 

 fourth pair (fig. 10) more slender and sparingly seti- 

 ferous, the joints of the outer branch dilated and 

 obliquely produced at the distal extremity, and 

 narrowed at the base ; fifth pair (fig. 11) three or four 

 times notched towards the extremity of the inner 

 edge, and bearing two short terminal setae; penulti- 

 mate abdominal somite rather shorter than the last, 

 which is partially divided so as to form two sub- 

 triangular segments (fig. 13). Caudal rami (Q.g. 10) 

 distant, nearly straight, about once and a half as long 

 as the last abdominal segment, bearing two very 

 minute apical hooks (fig. 14). Length nearly |-th of 

 an inch (3*3 mm.). 



This species is undoubtedly very nearly allied to, if 

 not identical with D. psyllus, Thorell, but the maxillae 

 and foot-jaws differ decidedly from those of that 

 species as described in M. Thorell's work. The 

 replacing of the spines of the third and fourth feet by 

 long setae, and the dentated margin of the last joint of 

 the inner branch of the mandible palp are dis- 

 tinctive characters, as also is the serrated outline of 



