ISOPODA. CRUSTACEA. PORCELLIO. 337 



than the last segment, like the European animal, a supposed varia- 

 tion from which, in this respect, caused Mr. Say to regard it as 

 distinct. But on comparison, ours corresponds with foreign speci- 

 mens, in every respect. This is the common Sow-bug of our 

 cellars and gardens. 



GENUS PORCELLIO. 



P. NIGRA, SAT; Journ. Acad. JVoi. &., i. 432. 



I think there can be little doubt that this is identical with P. sca- 

 6er, LATR. and Oniscus granulatus, LAM. 



P. LJEVIS, LATR.; Genera, i. 70. DESM.J FLEM. 



If the animal to which I refer is not this species, it is yet un- 

 described. 



These two species are also called Sow-bugs. The first is 

 found everywhere under stones, leaves, bark, &c. ; the second I 

 found in a cellar. 



GENUS L!GIA. 



One species has been observed about the timbers of a decaying 

 wharf. It seems to be smaller than L. oceanica. 



GENUS AS^LLUS. 



A. VULGA'RIS ? LATR. A species is common on sticks sub- 

 merged in ponds and ditches, which is much larger than either of 

 the species described by Mr. Say ; and I cannot find that it dif- 

 fers from the foreign species. 



GENUS IDOT^A. 



I. C(ECA, SAY ; Journ. Acad. Nat. Sc., i. 424. 



Found on sandy beaches, where it forms the little serpentine 

 tracks which are always noticeable soon after the recess of the 

 tide, and at one end of which the animal may be found with his 

 back loaded with sand. When the coming tide overtakes them, 

 they swim about with great activity. 



43 



