348 SYNOPTIC COLLECTION. 



hatched the crayfish resembles the adult in general char- 

 acters, though differing in details. The male of Cam- 

 barus has two forms and these are considered by Faxon 1 

 as alternating stages in the life of the same individual, 

 one phase being assumed through the breeding periods, 

 the other during the intervening seasons of sexual quies- 

 cence. Crayfishes abound in the middle and western 

 states, but few know that they are also found in Massa- 

 chusetts. The little creature seen in No. 850, Cambarus 

 bartoni Gir., came from a small brook in North Grafton 

 where for a number of years we obtained theni for pur- 

 poses of instruction. 



Another species of this genus is the blind crayfish, 

 Cambarus pellucidus Tellk. 2 (No. 851) found "in Mam- 

 moth Cave. Living under these unfavorable conditions 

 its body is smaller and the eyes which its ancestors pos- 

 sessed have gradually disappeared, although the eye- 

 stalks remain (Kingsley). 



Peculiar modifications of structure have taken place in 

 Galathea rugosa Fabr. (No. 852). The exoskeleton is 

 ridged and many of the ridges are provided with hairs. 

 The abdomen is shortened and tapers posteriorly, while 

 the cephalothorax has a swollen, puffed-out appearance. 

 The latter region is much darker in color at the anterior 

 end and this with the hairy ridges gives the crustacean 

 a hardy aspect. A distinct groove on each side of the 

 carapace divides this protecting covering into a median 

 and two lateral parts. The last thoracic segment is 

 not fastened to the others but is freely movable. 



The appendages of the cephalothorax like the body 

 are covered with hairs. The three pairs of small walk- 

 ing-feet extend forward and are provided with spikes 

 instead of claws ; the last pair are vestigial and are not 



iAmer. Journ. Sci., (3), XXVII, 1884, pp. 42-44. 

 3 Cambarus pellucidus Erichson. Smith, Rep. U. S. Comm. Fish 

 and Fisheries, i872-'73, p. 639. 



