325 



ever, of much larger size and more slender form of body, differing moreover very 

 conspicuously in the structure of the caudal setae, the middle of which, in Scott's 

 species, has the form of a comparatively short and stout lancet-shaped lamella. 



Occurrence. Several specimens of this form, males and females, were 

 found last summer at Korshavn in the same places where Cylmdropsyllus Icevis 

 occurred. 



Gen. 73. D'ArcythOHlpSOnia, Scott. 1906. 



Generic Characters. Body, as in the 2 preceding genera, slender cy- 

 lindrical in form, with rather soft, thin integuments. Rostral projection small, 

 not defined behind. Genital segment in female distinctly subdivided. Caudal 

 rami small, but with one of the apical setae much elongated. Anterior antennae 

 comparatively short, but composed of 7 well-defined joints, the 2nd not much 

 prolonged. Posterior antennae likewise more robust than in the preceding genera, 

 with the outer ramus very small. Mandibular palp small, uni-articulate. Maxillae 

 with an oval setiferous lamella outside, masticatory lobe rather coarse, intermediate 

 lobe apparently wanting. Anterior maxillipeds strongly built, with 2 short digiti- 

 form lobes inside the claw-shaped terminal joint. Posterior maxillipeds peculiarly 

 transformed and very small, each forming a vertical immobile lamella armed with 

 2 claw-like recurved spines, and having a small nodiform appendage outside, tipped 

 with a minute bristle. Natatory legs comparatively small, but with very long 

 apical setae, 1st pair only slightly differing from the others, inner ramus in all 

 pairs distinctly biarticulate. Last pair of legs very small and rudimentary. 



Remarks. This genus has recently been established by Th. Scott, to in- 

 clude the form previously described by him as Cylindropsyllus fairliensis. This form, 

 indeed, exhibits] several well marked differences in its structural details, both from 

 Cylmdropsyllus and Stenocaris, though its right to a place in the same family with them 

 is evident. The peculiar structure of the posterior maxillipeds has quite escaped 

 the attention of Th. Scott, who erroneously describes the anterior maxillipeds as 

 the posterior ones. 



Specific Characters. Female. Body very slender and flexible, cylindrical 

 in form, though a little wider posteriorly than anteriorly (the reverse of what is 



210. D'Areythompsonia fairliensis, Scott. 



(PI. CCXVII). 



lindropsyllus fairliensis, Th. Scott, in the Seventeenth Ann. Rep. of the Fishery Board for 

 Scotland, Part. Ill, p. 258, PI. X, figs 1114, PI. XI, figs 14. 





