BIOLOGICAL SURVEY OF WOODS HOLE AND VICINITY. 131 



V. AMPHIPODA. 



Locally, at least, the amphipods are by far the most abundant of the Malacostraca, 

 both in respect to the number of individuals and of species. Seventy-one determined 

 species are recorded for the region, to which number must be added 6 which are listed as 

 undetermined or are doubtfully to be included in this list. These species belong to 

 54(4-5?) genera and 22( + 2?) families. Of the total number of species recorded, 35, or 

 about one-half, have been taken during our own dredging operations; 26 others have 

 been identified from shore or townet collections made during the progress of the survey; 

 while the remainder are recorded solely upon the authority of published statements. 



None of the species encountered during the present work have been described as 

 new to science, though it is believed that the collections contain one or more unde- 

 scribed species. About nine species have been added to the fauna of the region either 

 through our dredging operations or through the identification of material in the posses- 

 sion of the laboratory. 



Verrill and Smith (1873) listed 31 species of amphipods, of which only 16 were 

 determined species recorded for specified localities within the region. Many of the 

 others must, however, have been observed in local waters, although the ranges were 

 stated in general terms. 



Holmes (1905) lists 79 determined species of amphipods, some of which were first 

 described in his report of that date. From this number, however, must be deducted 

 about 20 species which were not recorded for points within the area at present under 

 consideration. Miss Rathbun, in her "List of the Crustacea," includes over 100 species 

 and varieties for the whole of New England, but a considerable proportion of these are 

 extralimital as regards our present region. 



The list of invertebrates for eastern Canada comprises 7o( + 4?) species of amphi- 

 pods, a number almost identical with our own. Of these, 20 are known to be common 

 to the two lists. The Plymouth catalogue records 52 members of this order, of which 

 only 7 or 8 appear to be common to our Woods Hole fauna. Herdman catalogues 129 

 species for the Irish Sea, while Graeffe lists 49(4- 1 ?) for the Gulf of Trieste. 



Since the amphipods are contained very largely in the sand and mud brought up 

 by the dredge, the completeness of the record for any region depends, of course, upon 

 the character of the bottom sample obtained and upon the thoroughness with which it 

 is subsequently washed. Thus in the first season (1903) few amphipods were listed, 

 owing to the imperfect methods then employed. Another possible source of error is the 

 likelihood of free-swimming species from any depth being caught in the dredge during 

 the passage of the latter through the water after leaving the bottom. Thus, some of 

 those amphipods which constitute at times such an important element in the plankton 

 may figure as bottom dwelling species in the records. It is believed that cases of this 

 sort are comparatively few, however, owing to the probability that these free-swimming 

 species would pass out through the meshes of a dredge net. 



With a few exceptions no effort was made to identify the amphipods in the field, 

 but the specimens from each station were preserved for future determination. For 

 the identification of many of these we are under obligation to Prof. S. J. Holmes, to whom 

 we are likewise indebted for a critical examination of our check list of amphipods. The 

 greater part of the work of identification was, however, performed by Dr. Cole. A 



