354 U.S. NIATIONAL MUSEUM BULLETIN 271 



doubtedly congeneric with the type-species of Orchomenella, Anonyx 

 minutus Kr0yer, 1846 (original designation). Sars had incorrectly 

 identified Anonyx nanus and his material later was named Tryphosella 

 sarsi by Bonnier (1893); indeed Sars had in hand Anonyx nanus but 

 he erected for the material the name Orchomenella ciliata, later shown 

 by Stebbing (1906) to be a synonym of A. nanus. Unfortunately 

 Stebbing did not therefore synonymize Orchomenella with "Tryphosa," 

 since the two type-species were congeneric. Thus, Orchomenella must 

 fall to Tryphosa and all species of Tryphosa (auct.), so well known 

 since the time of Sars (1895) and Stebbing (1906) must be given a 

 different generic name, which is Tryphosella Bonnier. 



Epistome generally broadly lobate in front, occasionally acute, or 

 fiat and unproduced, lobe of upper lip generally prominent but rarely 

 projecting far in front of epistome; mandibular small, poorly ridged or 

 weakly setulose, palp attached proximal to molar; gnathopod 1 

 subchelate, article 6 longer than 5 ; telson variable, entire (Allogaussia) 

 or minutely and deeply cleft. See Lepidepecreum for intergrading 

 species. Species (including Allogaussia): 61+, cosmopolitan, cold- 

 water, littoral to abyssal. "Orchomenella" groenlandica (Hansen) is 

 treated in Keys L, N, O, and P as a distinct generic taxon. 



Pachychelium Stephensen 



Pachychelium Stephensen, 1925a. 



Type-species: P. davidis Stephensen, 1925a (original designation). 



Antenna 1 very stout, body slender; mandibular molar absent, palp 

 attached rather distally; maxilla 1 lacking palp; maxilla 2 with 

 vestigial inner plate; maxilliped lacking inner plate or inner plate 

 very small; gnathopod 1 enlarged, subchelate, article 6 large, ovate; 

 telson short, entire. Species: 3, bipolar, littoral to bathyal. 



Pachynus Bulycheva 



Pachynus Bulycheva, 1955. 



Type-species: P. chelatum Bulycheva, 1955 (original designation). 



Upper lip and epistome apparently not differentially produced; 

 mandibular molar absent, palp attached rather distally; maxillipedal 

 palp 3-articulate, or with a small fourth article, article 3 elongate 

 or not; gnathopod 1 chelate; telson short, entire. Species: 2, boreal 

 Pacific, littoral to bathyal. 



Paracallisoma Chevreux 



Paracallisoma Chevreux, 1903. 

 Type-species: P. alberti Chevreux, 1903 (original designation). 



