ISOPOD8 OF NORTH AMKKKU. <)V)8 



ANALYTiCAl, KEY TO TIIIO (iEXKKA OK THE FAMILY TKICHONISCID.T:. 



a. Eyes present. 



1>. Body not sculptured dorsally with lonjiitudinal ribs. Lateral parts of the tho- 

 racic segments not expanded. Second pair of antenn;e lonf;. Branches of the 

 uropoda tenninating in a hunch of hairs. Epignath of inaxillipeds narrow, 

 linguiform with a rounded expansion at tiie base. Abdomen abruptly nar- 

 rower than thorax ( Jeiuis Trirlioi) incus Brandt 



b^. Body sculptured dorsally with longitudinal ribs. Lateral parts of thoracic seg- 

 ments expanded. Second pair of antenuie short. I nner branch of the uropoda 

 terminating in a slender spine. Epignath of inaxillipeds simple, lanceolate. 

 Abdomen not abruptly narrower than thorax. .(Jenus Ilaplopldhabnus Schobl 

 a'. Eyes absent < ienus I'rackenndgia Ulrich 



126. Genus TRICHONISCUS Brandt." 



Body oblong. 



Head usually rounded in front, generally with small hut distinct 

 lateral lobes. 



Eyes small, distinct, composed of three ocelli. Second pair of anten- 

 nte generally long. 



Palp of maxillipeds with the four joints confluent; masticatory lobe 

 nearly as large as the palp and tei-minating in a narrow, ciliated lash; 

 epignath narrow, linguiform, with a rounded expansion at tiie base. 



Abdomen abruptly narrower than thorax; lateral parts of all the 

 segments visible, small. 



Terminal abdonnnal segment usually truncate at tip, and slightly 

 emarginate on each side. 



Legs long, slightly increasing in length posteriorly; joints furnished 

 with spines. 



Inner branch of the tirst pair of pleopods greatly produced and 

 bi-articulate in the nial(\ 



Basal article of uropoda broad and flattened, both branches termi- 

 nating in a ))unch of hairs. 



ANALYTICAL KEY TO THE srECUCS OF THE GENUS TRICHONISCUS. 



a. Surface of body smooth. Front of head straight with small lateral lobes. Last 

 three arti('les of second pair of antenn;e with the inner margins not beset with 

 tubercular-like papilhe. Terminal segment of abdomen with apex truncate. 



TrIcJtoinscus pusilliiti Brandt 

 aA Surface of body covered with low tuliercles. Front of head triangularly pro- 

 duced, \vith apex slightly emarginate; antero-lateral lobes large. Last three 

 articles of second pair of antenna' with the inner margins beset with tubercular- 

 like papillae, each surmounted with a tuft of short stiff hairs. Terminal seg- 

 ment of abdomen with apex rounded TVichonucus papillicornis Richardson 



«See Budde-Lund for characters of genus, Crust. Isop. Terrestria, 1885, p. 243, and 

 Sars, Crust, of Norway, II, 1899, pp. 160-161. 



