336 INVERTEBRATA OF MASSACHUSETTS. 



ment ; first two segments nearly as long as the three next, and 

 about one third of the whole length ; on the middle of the first is 

 a spine ; two last segments short and heart-shaped. Hands hav- 

 ing a long curved finger ; an imperfect thumb on the second pair 

 of legs ; a tubercle at the base of the ovate carpus, and a small 

 spine at the middle. This might be called C. sanguinea, from its 

 color, which it retains in spirits. 



These curious animals are found among clusters of zoophytes 

 and delicate sea-weeds. Their mode of walking is like that of 

 some caterpillars, who bring the tail forward to the head and then 

 thrust the body forward its whole length to prepare for another 

 step. 



ISOPODA. 



The animals included under this division are small, and many 

 of them well known. They have seven pairs of legs, similar in 

 shape, and nearly equal in length, all of them constructed for 

 walking alone. They live on land, and in both fresh and salt 

 water. They may be distributed into three natural families ; 

 1. CloportidcR, which are terrestrial, and well known under the 

 names of Sow-bugs, Pill-bugs, &c. Their food is decaying vege- 

 table matter. 2. Cymothoadce, which are parasites, and live for 

 the most part about the gills of fishes, from which they suck their 

 nourishment. 3. Idot&idce, those which live in the water, but 

 are not parasites. 



GENUS ARMADILLO, LATR. 



A. PILULA'RIS, SAY ; Journ. Acad. Nat. Sc., i. 432. 



I have had no opportunity to compare this with any European 

 species. It is commonly called the Pill-bug, and is very com- 

 mon in gardens and cellars, under stones and boards. 



GENUS ONISCUS, LIN. 



O. ASE'LLUS, LIN. ; LATR. ; DESM.; Consid., 320, pi. 49, f. 5. O. raura- 

 rius, FABR. ; Cuv. O. affinis, SAY ; Journ. Acad. Jfat. Sc., i. 430. 



In all the specimens I have examined, the styles are longer 



