176 



Gen. 4. PorcelllO, Latr., 1804. 



Generic Characters. Body oval, more or less depressed, with the lateral 

 parts lamellarly expanded. Cephalon partly flanked by the side-plates of the 1st 

 segment of mesosome, lateral lobes well developed, frontal lobe more or less 

 projecting, and distinctly defined from the epistome. Metasome not abruptly con- 

 tracted, epimeral plates of 3rd to 5th segments prominent and recurved; last 

 segment conically produced. Eyes, as a rule, well developed, subdorsal. An- 

 tennae moderately slender, with the flagellum composed of 2 articulations only. 

 Oral parts normal. Legs gradually increasing in length posteriorly, last pair in 

 male sometimes slightly differing from that in female. Opercular plates of the 

 2 anterior pairs of pleopoda, and sometimes also of the 3 succeeding pairs, pro- 

 vided with distinct air-cavities. Copulative organs of male of a similar structure 

 to that in Oniscus. Uropocla distinctly projecting, outer ramus lanceolate, inner 

 much smaller, linear, and originating far in front of the former. 



Remarks. The present genus was established as early as in the year 

 1804 by Latreille. It is chiefly distinguished from the 3 preceding ones by the 

 Inarticulate antennal flagellum, and by the opercular plates of the 2 anterior, or 

 of all pairs of pleopoda having distinct air-cavities (pseudo-tracheae). Otherwise this 

 genus is very nearly allied to Oniscus. The genus comprises numerous species 

 from all parts of the world, no less than 62 species being described in the work 

 of Mr. Budde-Lund, and 18 others, not examined by him, being enumerated; 

 whereby the number of as yet known species amounts to 80 in all. In the fol- 

 lowing pages, 6 species will be described. 



, 4 



1. Poreellio scaber, Latr. 



(PI. LXXVII.) 

 Poreellio scaber. Latreille, Hist. nat. des Crustaces et des Insectes, Vol. VII, p. 45. 



Syn: Oniscus granulatus, Lamck. 



Poreellio niger, Say. 

 Bmndtii, M.-Edv. 



dubius, Koch. 



asper, Koch. 



Montezumce, Sanss. 



,, paulensis, Heller, 



Specific Characters. Body oblong oval, about twice as long as it is broad,' 

 dorsal face slightly convex and very rough, owing to the presence of numerous rounded 

 tubercles. Cephalon with the lateral lobes rather large and rounded, frontal lobe less 

 prominent, obtusely triangular. Side-plates of mesosome .of moderate size, with 



