736 CRUSTACEA. 



thoracic segment, and forms a semicircle beyond it. Last abdominal 

 segment smallest ; third, fourth, and fifth segments much produced 

 backward on either side. Surface of thorax and abdomen with a few 

 very short scattered spinules. 



If this is a distinct species, it is also a new genus, the seventh pair 

 of legs being of full size ; and it may be named the Actcecia eucliroa, 

 the name by which it was designated by the author in his earlier 

 manuscripts. 



Plate 48, fig. 6 a, animal, enlarged three diameters; b, outline of 

 back ; c, outline of front of head; d, abdomen in outline, upper view; 

 e, antenna, enlarged ; /, outer maxilliped ; g, extremity of one of 

 the legs ; h, caudal appendages, under view. 



Genus STYLONISCUS, Dana. 



Oculi mediocres. Antennae ad articidationem 6tam geniculate, flagello 

 multiarticulato, elongato. Styli caudales ac in Oniscinis. Pedes 

 septimi vix minores, non debiles. 



Eyes of moderate size. Antennse geniculate at the fifth articulation, 

 flagellum multiarticulate, elongate. Caudal stylets as in the Onis- 

 cince. Feet of seventh pair of full size. 



The species of this genus approach the Lygiae in form, and one of 

 the two here described has the base of the stylets oblong and project- 

 ing much behind the abdomen. The last abdominal segment does not 

 project backward between the caudal appendages. The head is not 

 set deeply into the next segment, as in the Porcellios, and has the 

 posterior margin little arcuate. 



Styloniscus magellanicus. 



Corpus nitidum, anguste ettipticum, anticd rotundatum. Abdomen tho- 

 race subito paulo angustius, oblongum, segmento seeundo brevissimo, 

 ultimo non longiore quam penidtimum. Caput segmento proximo 

 paulo brevius et paulo angustius. Styli caudales divaricati, fere abdo- 



