318 



Gen. 70. ArthrOpSyllllS, G. 0. Sars, ii. 



Generic Characters. Body without any dorsal or sub-dorsal processes, 

 but flanked on each side by a uniform series of acutely produced lappets arising 

 from the lateral parts of all the segments except the last 2. Cephalic segment 

 rather broad, and produced in front to a broadly triangular rostral projection, 

 antero-lateral corners rounded off. Anterior antennae less slender than in the 

 preceding genera, and in female composed of only 3 joints; those in male strongly 

 hinged. Posterior antennae likewise rather robust. Oral parts exhibiting the 

 structure characteristic of the family. Natatory legs with the 2nd basal joint 

 less produced than in the 3 preceding genera, 1st pair with both rami biarticu- 

 late and subequal in size. Inner ramus of the 3 succeeding pairs well developed, 

 biarticulate, though shorter than the outer ; that of 2nd pair slightly transformed 

 in the male. Last pair of legs of normal appearance, with the distal joint 

 slender and narrow, proximal joint with a well-defined setiferous expansion inside, 

 wanting however in male. 



Remarks. This genus, like the 3 preceding ones, is based upon a single 

 species, which in spite of the rather different external appearance of the body, 

 in all anatomical details exhibits a near relationship to those genera, and more 

 particularly to the typical genus, Anchorabolus. The generic name here proposed 

 refers to the sharp demarcation of the segments, due to the acutely produced 

 lateral parts. 





207. Arthropsyllus serratus, G. 0. Sars, n. sp. 



(PI. CCXIV). 



Specific Characters. Female. Body moderately slender and somewhat 

 depressed, tapering gradually behind, with all the segments very sharply defined. 

 Cephalic segment consparatively broad, and about the length of the 3 succeeding 

 segments combined, rostral projection triangular, broad at the base and terminating 

 in 2 small prominences, dorsal face of the segment smooth and slightly vaulted, antero- 

 lateral corners evenly rounded, lateral edges each exhibiting beyond the middle a small 

 notch, and behind it produced to an acute lappet pointing obliquely backwards. Each 

 of the 4 succeeding segments produced on each side to a similar, though somewhat 

 larger lappet. Urosome somewhat shorter than the anterior division, and provided 

 with 3 pairs of lateral lappets similar to those on the anterior part of the body, 

 though somewhat diminishing successively in size, the 2 posterior segments being 



