REPORT ON THE AMPHIPODA. 1593 



Locality— July 4, 1875, North Pacific; lat. 3G° 42' N, long. 179° 50' W. ; surface, 

 night ; surface temperature, 69° *2. One specimen, young male. 



Remarks. — Claus' specimen from Zanzibar was a young male, only 6 mm. in length ; 

 the representation of the first gnathopods in Claus' figure is not suitable to those of the 

 Challenger specimen, but, as they are. not separately figured, I have not allowed this 

 difference to outweigh the general agreement between the two forms. 



Genus Leptocotis, Streets, 1877. 



1871. Oxycephalus (pars), Claus, Unters. liber den Bau und die Verwandschaft der Hyperideii, 



Nachriehten K. Gott. Soc, p. 155. 



1877. Leptocotis, Streets, Bulletin U.S. Nat. Mus., No. 7, p. 136. 



1878. „ Streets, Proc. Acad. Nat. Sci. Pliilad., p. 283. 



1879. Oxycephalus (pars), Claus, Die Gattungen und Arten der Platysceliden, p. 48. 



1887. Leptocotis, Bovallius, Systematical List of Amph. Hyper., Biliang till K. Svensk. Vetensk.- 



Akad. Hand]., Bd. 11, No. 16, p. 38. 

 1877. Oxycephalus (pars), Claus, Die Platysceliden, p. 71. 



For the original definition of the genus, see Note on Streets, 1877 (p. 470). In 

 the definition given the following year Dr. Streets omits the statement that the con- 

 stricted portion of the head is " not narrower than the thorax," and applies the term 

 " thoracic legs " to the gnathopods and peraeopods in common, instead of to the 

 perseopods alone as in the earlier definition. The first species clearly known of this 

 genus is Claus' Oxycephalus tenuirostris, which Claus retains under Oxycephalus, making 

 Leptocotis spinifera, Streets, a synonym of it, The differences, indeed, between 

 Oxycephalus and Leptocotis as defined by Dr. Streets resolve themselves almost entirely 

 into the comparative stoutness of the former and slenderness of the latter genus. Of 

 Oxycephalus Dr. Streets says, " body moderately long, robust ; head narrow, produced 

 anteriorly in a broad, triangular rostrum, short, grooved below ; " " the last three pairs 

 [of Perseopods'] with the basal joint broadly dilated ; " " the sixth abdominal segment 

 broad, not elongated ; the caudal appendages short, broadly lanceolate ; telson broadly 

 triangular." For Leptocotis he says, " body long and slender ; head produced 

 anteriorly to the superior antennae in a long, slender rostrum;" "the last three pairs 

 [of Perseopiods] with the basal joint dilated ; " " the sixth abdominal segment (the 

 fifth and sixth fused) elongated ; the caudal appendages long, linear ; telson long, 

 triangular at apex." In regard to Oxycephalus he also says, " extremity of the sixth 

 pair [Fourth Perseopods] — articulating with the broad basal joint — finely serrated 

 along the anterior margin," but this equally applies to Leptocotis. Of Leptocotis he 

 says that the upper antennae are " curved in the male," but this also ajyplies to 



(ZOOL. CUALL. ESP. — PART LXVII. — 1888.) Xxx 200 



