G64 PROCEEDINGS OF TIJE NATIONAL MUSEUM. 



2)ulmllatus, which seems very probable, but owing to the unsuspected 

 existence of numerous related species this opinion may possibly need 

 revision. 



Genus HADROBOLUS Cook. 

 Jladroholus Cook, Bniudtia, 18it7, p. 73. 



This ji'cnus is distinct ft'om J'nchyholus in the following characters: 



1. The sternum of tlie copiilatory legs is very broad and short, being 

 scarcely ])ro(luced in the miildlc. 



2. The posterior lamella' are widely Ne[)aratcd, while in Fachyholus 

 they arc crowded inesad by the Magella, whi(^h emerge outside (laterad) 

 of the apices of the posterior liiminav 



'A. The tiagella are much shorter and moie robust, i)rovi(led near the 

 middle with a large blunt spine; they are also distally fleshy and have 

 a very large seminal aperture surrounded by a finely incised membran- 

 ous iringe. in l*nchiihohis the seminal a])ertur<^ is a small round open- 

 ing in the entirely cornerous an<l simi)le ajjcx of the ilagellum. 



4. The last Joint of the legs of males is greatly elongated at the 

 expense of the jjcnultimate, which is thus much smaller than the ])re- 

 ceding (fourtli) Joint. In Fuchyholns Joints 4 and ;"> are sube(iual, and 

 the last Joint is relatively shorter; that is, not longei- than 4 and 5 taken 

 together. 



5. The jiad of the last Joint of the legs of males is oblong and extends 

 the whole length of the Joint, the subterminal bristles being farther 

 apart than in raelri/holiis, in which the pad is somewhat oval in shape 

 and does not extend beyond these two bristles, which are located a 

 considerable space below the apex of the joint. 



6. The pads also probably fun(!tion in a diffeient manner in the two 

 genera, as in lladroholus they are fleshy througiiout, the sides beifig 

 scarcely chitinized and tho surface being convex or irregularly shrunken. 



In Pacln/boluii,\)U the contrary, the sides of the pad are much more 

 l)rominent, strongly chitinized, and dark colored, while the surface is 

 also of firm texture and always uniformly and strongly concave. It is 

 not impossible that this surface can be retracted by muscles a)id thus 

 secure adhesion by suction, so to speak. 



Sui)erticially there are comparatively slight differences, such as the 

 somewhat more skMider habit and distinctly thinner armor. The anten- 

 na' are also distinctly more slender than in Pavhybohis, and the first 

 segment has laterally its anterior nuirgin defined by a distinct fine suU'us, 

 which on rachyholiis, is obsolete or, if traceable, is much closer to the 

 margin than in lladrohohiH. 



HADROBOLUS CRASSICOLLIS (Peters). 



(inato LIT, lijjs. 2a-2ii.) 



tspirohohts crassicoUin 1'ktkus, Monatsber. k. inenss. Akad. Wiss., Berlin, 18r>r>, p. 



Tit; Kciso iiacli iMozaiul)i<nio, /ooloj^y, 18(52, p. 'AS, pi. xxxiv, lig. 8. 

 iJa(iroh:)lm cnixsivoUis Cook, Braiultia, 1897, p. To. 



