ON THE AMPHIPOD GENUS LEPTOCHEIRUS. 561 



PAPERS. 



26. On the Ainphipod Genus Leptocheiriis. 

 Bj E. W. Sexton, Marine Biological Laboratoiy, Plymouth*. 



[Received December 22, 1910 : Read March 21, 19U.] 



(Plates XVIL-XIX.t, and Text-f]gure 146.) 



The genus Leptocheirus wns instituted by Zaddach in 1844, with 

 the type species L. pilosas. So much discussion has arisen over 

 this species that it seemed desirable to settle the inatter by refer- 

 ence to the actual specimens, should it prove possible to trace them. 

 Dr. Braun, in whose keeping at the Konigsberg Museum they were 

 discovered, most kindly sent them to me for examination and also 

 granted pei-mission to dissect and figure one of the specimens, so 

 that the vexed question might be finally set at rest. I am deeply 

 indebted to him, and to all those also who have so generously 

 assisted me in this investigation : to Canon Norman, for the loan 

 of specimens of L. subsalsios, pinguis, hirsutimanus, guttatus, and 

 peclinatios ; to Monsieur Chevreux for specimens of L. cornuau?'ei, 

 ti'icrisiatits, and dellavallei ; to Dr. Kiikenthal and Dr. Zimmer for 

 permission to examine Grube's specimens of Protomedeia Im^suti- 

 ma7ia ? and P. guttata ; to Dr. Hjalmar Theel and Dr. Holmquist 

 for the trouble they have taken in searching for Ohiin's specimen 

 of L. aherixons ; to Professor Steuer for his assistance in tracing 

 Heller's specimen of P. /m-sutimana ; to Dr. Otto Pesta for the 

 description and figures of this same specimen, by which its 

 identification became possible ; and to Professor Vayssiere and 

 Monsieur Collin, of Cette, for the help given in searching for 

 Catta's specimen of massiliensis. 



It will be noted that the number of species has been reduced. 



L. corniuiurei Sowinski and subsalsics IS^orman become synonyms 

 of the type species, the one being the full-grown male, and the 

 other the full-grown female. Norman's recoixl is very interesting 

 with regard to the distribution, confirming Zaddach's account, 

 both being for fresh or almost fresh water. All the other species 

 of the genus, so far as yet known, are marine. 



I have also shown, I hope conclusively, the identity of 

 L. pecthiMus Norman with L. dellavallei iStebbing, which indeed 

 Mr. Walker has always maintained. L. pectinatas is, in my 

 opinion, the young form sexually mature but not full-gi'own, 

 while L. dellavallei is the fully developed animal. Figures are 

 given of the characters on which Chevreux (16) p. 91, and 

 Norman (36) pp. 87, 88, separated them, to prove that the 

 differences ai-e merely those due to sex and development. The 

 question of distribution is also discussed by these authors in 

 separating the species, pectinatus having always been found near 

 the shore, and dellavallei at greater depths, but our present 



* Communicated by Dr. W. T. Calm an, F.Z.S. 

 f For explanation of the Plates see p. 593. 



