248 U.S. MATIONAL MUSEUM BULLETIN 271 



1-2 densely setose medially; gnathopods slender, feeble, poorly sub- 

 chelate; iiropod 3 not exceeding uropod 1, rami equal, lanceolate, 

 outer 1-articulate; telson entire; body lacking dorsal teeth or spines. 

 Species: 2, arctic, littoral. 



Haustoriidae 



Figures 97-100 



Diagnosis. — Antenna 1 usually with accessory flagellum; rostrum 

 usually absent but when present then pereopod 5 longer than 4; otherwise 

 pereopod 5 shorter and of different structure than pereopod 4; pereo- 

 pods strongly spinose and setose (fossorial); gnathopods feeble. See 

 Gammaridae, Phoxocephalidae, Liljeborgiidae, Ampeliscidae, Param- 

 phithoidae, Astyridae, Argissidae. 



Description. — Accessory flagellum absent (rare) or 1- to multi- 

 articulate; peduncles of antennae elongate or not; antenna 2 peduncle 

 occasionally spinose, often wdth elongate plumose setae; rostrum 

 usually inconspicuous, occasionally present; upper lip not strongly 

 incised; mandible always with 3-articulate palp and molar rarely 

 absent but often nontriturative; lower lip with inner lobes; maxillae 

 basic; maxilliped Avith well-developed plates, palp 3-4 articulate, occa- 

 sionally of peculiar shape; gnathopods feeble, varying from minutely 

 chelate, through simple to lacking article 7; coxae of medium length 

 or long, highly variable, occasionally acuminate; uropod 3 variable 

 but one or both rami longer than or equal to peduncle, lanceolate, 

 rectangular, or subcylindrical, rarely flabellate; telson short or medium 

 in length, deeply cleft or subentire. 



Relationship. — The family is so neatly linked to the Gammaridae 

 by the genera Pontoporeia and Bathyporeia that on gross morpho- 

 logical grounds there seems little reason to maintain it; nevertheless 

 taxonomists seem to have been able to recognize its members (ex- 

 cepting Euxinia Tucolesco). Of particular significance are the feeble 

 gnathopods of haustoriids and the strong development of spines and 

 setae for these digging animals. Certainly the fossorial habit dis- 

 tinguishes them from most Gammaridae. 



Liljeboriids have a weak mandibular molar, poorly spinose append- 

 ages and very powerful gnathopods. 



Priscillina and Haustorius resemble the Paramphithoidae through 

 their subacute first four coxae but the excessive spination and seta- 

 tion of appendages and multiarticulate accessory flagella are distinc- 

 tive of Haustoriidae. 



The Phoxocephalidae are closely related and merge into Haus- 

 toriidae through genera such as Platyischnopus and Zobracho. Most 



