98 CARL BOVALLIUS, AMPHIPODA HYPERIIDEA. I. 2. HYPERIIDjE. 



Hyperoche Luetkeni. 



1887. Hyperoche medtisariim, (H. KEOEYER.) H. J. Hansen. »Oversigt over det vestlige Granlands 



Fauna af malakostrake Havkrebs- 

 dyr», p. 56. Vidensk. Meddel. fra 

 den Naturhist. Forenihg i KJ0- 

 benhavn, 1887. 



It being impossible to unite the species described here as Hyperoche Luetkeni 

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

 pose for it a new specific name; then I had examined only female specimens, supposing 

 that the animal described here below as the male of H. Luetkeni was a separate spe- 

 cies. Since that time the study of young specimens of the male has convinced me 

 that the form in question belongs to Hyperoche Luetkeni; there are, however, many 

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

 rences until intermediate forms were found 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 antennae and the peraeon left aside; 



l:o. The form and armature of the first two pairs of perasopoda, 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 serration, 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 only the hind 

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

 teeth on the front margin more 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-fish, 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 peraeopoda, being veiy 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 breadth 

 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 males are narrower than those 

 in the adult ones. 



I am not able to find any greater differences between Hyperoclie cryptodactylus, lately 

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

 succeeded to prove that the dactylus of the second pair of peraeopoda is retractile, as it 



