98 OARL BOVALLIUS, AMPHIPODA HYr-RRIIDEA. I. 2. HYPERIID^. 



ffyperoche Ltiethe.ni. 



1887. Hyperoche mediisanim, (H. KROEYER.) H. J. Hansen. uOversigt över det vestlige Gr0nlan(ls 



Fauna af malakostrake Havkrebs- 

 dyr», p. 50. Vidensk. Meddel. fra 

 den Naturhist. Poreiiino' i KJ0- 

 benhavn, 1887. 



It being impossible to iinite the species described here as Hyperoche Lnetkeni 

 neither with Hyperoche. Kroeyeri nor with H. nlrt/ssorum, A. Boeck, I was bound to pro- 

 pose for it a uew specific naine; then I had exainined only female specimens, supposing 

 that the animal described here below as the niale of H. Lnetkeni was a separate spe- 

 cies. Since that tiine the stndy of young specimens of the niale has convinced me 

 that the form in question belongs to Hjqieroche Lnetkeni; there are, however, manj 

 small differences between the adult animals, not easily suspected to be only sexual diffe- 

 rences until interrnediate forms were fonnd to exist in the young animals. 



The most striking discrepancies between the fullgrown males and females are, the 

 common sexual difference in form of the antennas and the persBoii left aside; 



1:0. The form and armature of the iirst two pairs of pera^opoda, viz; in the male 

 the form of the carpus and its process is more slender, and the armature of the front 

 margin of the process consists of a normal sensation, the teeth pointing slightly downwards. 

 In the female the carpus and its process is more robust, with bulging sides, and the 

 armature of the front margin of the process consists of a row of broad, almost truncated 

 teeth, pointing forwards or rather a little upwards. The morphological explanation of this 

 feature is simple enough, the male form of the carpus being the primary onl}' the hind 

 part of the female carpus has increased thus bulging out and puUing the bases of the 

 teeth on the front margin moi'e downwards, thus producing a more powerful grasping 

 organ of the prehensile hand in the female, than of that in the male. The female needs 

 such an instrument more than the male because she, at least during the breeding-time, 

 seeks shelter in a yellow-iish, using probably the first two pairs of pera^opoda as a kind 

 of grasping organ. 



2:o. The form of the femur of the last three pairs of perfeopoda, being verj' narrow 

 and linear in the female, and somewhat dilated, more or less ovate, in the male. The 

 reason of this difference is also, I think, connected with the different manner of living of 

 the both sexes; the female, secluded within the cavity of a yellow-fish, has not much use 

 for the walking legs, and thus the tensor- and flexor-muscle of the femur remain less 

 developed than in the fullgrown male, living free. In the young male the relative bi-eadth 

 of the femur is scarcely greater than in the fullgrown female. 



3:o. The urus and its appendages are relatively more broad in the male than in 

 the female; also this feature may depend on the different mode of living of the both 

 sexes, as the peduncles of the uropoda in the very young niales are narrower than those 

 in the adult ones. 



I am not able to find any greater differences between ffyperoclie cryiitodactylus, lately 

 described by Stebbing, 1. c. p. 1399, and the male of H. Luetkeni, but as I have not yet 

 suceeeded to prove that the dactylus of the second pair of perteopoda is retractile, as it 



