BIOLOGICAL SURVEY OF WOODS HOLE AND VICINITY. 141 



prevalence in the middle of the Sound near the western end. The bottom here is largely 

 of clean sand and many typical sand-dwelling species, such as Echinarachnius parma 

 and various flounders, consequently flourish in this area. Cancer borealis and Pagurus 

 acadianus , on the other hand, are probably limited to the deeper waters on account of 

 the lower temperatures prevalent there. The latter species was taken only four times 

 by the Phalarope, though dredged at 41 of the Fish Hawk stations in Vineyard Sound. 



Among our local decapods we find a number of cases where interesting differences 

 of habitat are displayed by the various species within a genus. Only a few such may 

 be mentioned here. The differences in habitat shown by the two local members of the 

 genus Cancer have already been referred to. These differences seem to relate to tem- 

 perature, depth (if this is really an independent factor), and perhaps to character of 

 bottom. One Libinia (L. emarginata) is of almost universal occurrence throughout 

 both the Bay and the Sound ; the other (L. dubia) appears to be restricted to shallow, 

 inclosed waters. Although it is known to be abundant at some of these points, we do 

 not have a single authentic record of its occurrence in the dredgings. a The difference 

 displayed by the various local representatives of the genus Pagurus have likewise been 

 discussed in another connection. The almost complementary character of the distribu- 

 tion patterns for P. acadianus and P. annidipes is especial!} 7 to be noted. 



The following decapods were taken with the dredge during the operations of the 

 Survey. The asterisk, as usual, denotes species which were recorded from 10 or more 

 dredging stations. For all of these, charts have been plotted. 



Pandalus montagui. 



Pandalus leptocerus. 



Hippolyte zostericola. 



Spirontocaris groenlandica. 



Spirontocaris pusiola. 

 *Crago septemspinosus (chart 107). 

 *Homarus americanus (chart 108). 



Callianassa stimpsoni. 

 *Pagurus pollicaris (chart 109). 

 *Pagurus acadianus (chart no). 

 *Pagurus longicarpus (chart in). 



Pagurus kroyeri. 

 *Pagurus annulipes (chart 112). 



Heterocrypta granulata. 



Hyas coarctatus. 



Grouping, as usual, the more prevalent species according to the extent of their 

 known range upon our coast, 6 we have — 



Predominantly northern forms . 



Homarus americanus Labrador to New Jersey. 



Pagurus acadianus Grand Bank of Newfoundland to the mouth of Chesapeake Bay. 



(Northern?). 



o A few small specimens were thus identified at first, but further quite extensive collecting has thrown doubt upon these 

 determinations. 



6 We are indebted to Miss Rathbun for these statements as to range. 



*Pelia mutica (chart 113). 

 *Libinia emarginata (chart 114). 

 PLibinia dubia (very young). 

 *Cancer irroratus (chart 115). 

 *Cancer borealis (chart 116). 

 PCallinectes sapidus (fragment). 

 *Ovalipes ocellatus (chart 117). 



Panopeus herbstii. 

 *Neopanope texana sayi (chart ir8). 



Hexapanopeus angustifrons. 

 ^Pinnotheres maculatus (chart 119). 



Pinnixa chaetopterana. 



Pinnixa sayana. 



Dissodactylus mellitse. 



