ISOPOD9 OF NORTH AMERICA. ()93 



ANALYTICAL KEY TO THE GENERA OF THE FAMILY TRICHONISCID^E. 



a. Eyes present. 



ft. Body not sculptured dorsally with longitudinal ribs. Lateral parts of the tho- 

 racic segments not expanded. Second pair of antenme long. Branches of the 

 uropoda terminating in a bunch of hairs. Epignath of maxillipeds narrow, 

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

 rower than thorax Genus Trichoniscus Brandt 



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

 ments expanded. Second pair of antenme short. Inner branch of the uropoda 

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

 Abdomen not abruptly narrower than thorax. .Genus Haplophthalmns Schobl 

 a' '. Eyes absent Genus Brackenridgia Ulrich 



126. Genus TRICHONISCUS Brandt." 



Body oblong. 



Head usuall}' rounded in front, generally with small but distinct 

 lateral lobes. 



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

 nae generally long. 



Palp of maxillipeds with the four joints confluent; masticatory lobe 

 nearly as large as the palp and terminating in a narrow, ciliated lash; 

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



Abdomen abruptly narrower than thorax; lateral parts of all the 

 segments visible, small. 



Terminal abdominal 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 first pair of pleopods greatly produced and 

 bi-articulate in the male. 



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

 nating in a bunch of hairs. 



ANALYTICAL KEY TO THE SPECIES OF THE GENUS TRICHONISCUS. 



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

 three articles of second pair of antenme with the inner margins not beset with 

 tubercular-like papilla?. Terminal segment of abdomen with apex truncate. 



Trichoniscus pusillus Brandt 



a' '. Surface of bpdy covered with low tubercles. Front of head triangularly pro- 

 duced, with 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 Trichoniscus 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. 



