BIOLOGICAL SURVEY OF WOODS HOLE AND VICINITY. 1 33 



With the exception of those four species comprised in the last two lists, the amphi- 

 pods, when recorded from Buzzards Bay at all, were nearly always taken in the vicinity 

 of land, i. e., at the adlittoral stations. In a large proportion of cases the Bay stations 

 were near the passages connecting with Vineyard Sound, or close to the lower end of 

 the Bay.° 



On the other hand, even within the Sound, certain species are found not to have 

 an unrestricted distribution. For example, Haustorius arcnarius, Byhlis serrata, 

 Calliopius Iceviusculus , Pontogenia inermis, and Jassa marmorata are in large degree 

 restricted to the western half of the Sound, while Lysianopsis alba, Baiea scciinda, and 

 Auionoe smithi are for the most part restricted to the eastern half. One of the two 

 predominantly Bay-dwelling species {Ampelisca macrocephala) and perhaps also the 

 other {Plilocheirus pinguis) appear to be in some measure restricted in the Sound to 

 points where the bottom is muddy. The difference between the Bay and the Sound 

 in respect to tneir amphipod faunas, and in considerable measure the local distribution 

 within each of these bodies of water, are for the most part explainable by reference 

 to the character of the bottom. Just such types of distribution have already been 

 encounteied in the case of other groups and need not be discussed here. Certain cases 

 which appear to be explainable by reference to temperature will be considered shortly. 



An interesting feature respecting the amphipod life of the Bay and the Sound 

 appears when we consider the average number of species taken per dredge haul for 

 each body of water and for each vessel. The figures are as follows: 



Vineyard Sound; 



Fish Hawk i. 8 



Phalarope i. g 



Buzzards Bay: 



Fish Hawk i. 3 



Phalarope 1. 1 



While these figures were considerably higher for the Sound stations than forthe 

 Bay stations, there is nothing like the disproportion which might have been expected 

 in view of the fact that the number of predominantly Sound-dwelling species which 

 were shown upon our charts was so much in excess of (7J--2 times) the number of 

 predominantly Bay-dwelling species. 



Again, the average number of species per dredge haul is the same (1.6) for each of 

 the three types of bottom distinguished. And when we consider the lists of "preva- 

 lent" species for the various groups of stations, we find that only such one (Unciola 

 irrorata) occurred at one-fourth of the Vineyard Sound stations of the Fish Hawk, 

 while three species {Ptilocheirus pinguis, Unciola irrorata, and Ampelisca macrocephala) 

 occurred at an equal proportion of Buzzards Bay stations. This condition seems to be 

 only explainable on the supposition that while the number of species which inhabit 

 Vineyard Sound is greatly in excess of the number found in Buzzards Bay, such 

 species as do occur in the latter are of much more general prevalence throughout its 

 extent. A discussion of similar phenomena has already been given in chapter iii. 



Two apparent cases of distribution in relation to temperature are Calliopius IcEvius- 

 culus and Pontogenia inermis, which occur, so far as our dredging records show, primarily 



o In some cases, just without. Here and elsewhere stations have been classed as Bay or Sound stations which lay on the Bay 

 or Sound sides, respectively, of Sow and Pigs Reef, extending from the end of Cuttyhunk Island. 



