BIOLOGICAL SURVEY OF WOODS HOLE AND VICINITY. 97 
immugrants of recent standing can not be stated. We have no satisfactory evidence 
that such is the case. 
The Canadian list prepared by Whiteaves includes 66 Hydrozoa, 5 Scyphozoa, 44 
Actinozoa, and 4 Ctenophora. Of these, 41 Hydrozoa, 2 Scyphozoa, 4 Actinozoa, and 
4 (all) of the Ctenophora are common to our Woods Hole list. It is interesting that 
while the number of hydroids in the Canadian list is only half as great as in our own, 
the number of actinians is about three times as great. 
The catalogue for Plymouth includes 121 Hydrozoa, 8 Scyphozoa, 34 Actinozoa, 
and 3 Ctenophora. Of these, 34 (+6?) Hydrozoa, 2 (?) Secyphozoa, (2+1?) Actinozoa, 
and 2 Ctenophora are known to be common to the Woods Hole region. 
The list of Herdman for the Irish Sea comprises 129(+ 1?) Hydrozoa, 6 Scyphozoa, 
24 Actinozoa, and 4 Ctenophora. There is a rather close agreement between the 
Woods Hole, Plymouth, and Irish Sea lists in respect to the number of Hydrozoa 
comprised. On the other hand, both of the latter lists agree in including a considerably 
greater number of actinians than have been recorded from the Woods Hole region. 
For the Gulf of Trieste, Graeffe catalogues 64(+2?) Hydrozoa, 9 Scyphozoa, 29 
Actinozoa, and 5 Ctenophora. 
In all these comparisons the differences in area and in bathymetric range among 
the various regions must af course be kept in mind (see p. 87). 
On the average 1.8 species of ccelenterates were recorded for each of the 458 regu- 
lar stations of the Survey. The species found to be of most general occurrence was the 
coral A strangia dane, which was encountered at 158 of the stations, this being the only 
ccelenterate which was so prevalent as to be recorded from one-fourth of the stations 
dredged. It is likely, however, that Hydractinia echinata was actually present in at least 
one-fourth of the dredge hauls, and that it was frequently overlooked by us in listing 
the species in the field. 
Referring to the table on page 78, it will be seen that on the average nearly three 
times as many species of hydroids per dredge haul were recorded for the Fish Hawk 
stations in Vineyard Sound as for those in Buzzards Bay, while the average number of 
Actinozoa was the same in both bodies of water. The Phalarope stations in Vineyard 
Sound likewise show an excess of hydroids as compared with the stations in the Bay. 
From the table on page 79 it is evident that there is a greater wealth both of hydroids 
and of actinians on bottoms of gravel and stones than upon bottoms of mud or of 
pure sand. As respects Hydrozoa, the average number of species is nearly twice as 
great upon sandy bottoms as upon muddy ones. The distribution of most ccelenterates 
upon the local sea floor is, we believe, almost wholly conditioned by the character of 
the bottom. 
Charts have been prepared showing the distribution, in local waters, of 10 species 
of Hydrozoa and 3 of Actinozoa. A list of these, with a statement of the geographical 
distribution of each is given below. Owing to the probable incompleteness of our 
earlier records for the Hydrozoa, the practice of basing our charts upon the original 
dredgings of the ‘‘regular”’ series only has not been adhered to for this group. The 
results of various supplementary dredgings (see p. 62) have been incorporated here 
as in the case of the Foraminifera and the Bryozoa. 
16269°—Bull. 31, pt 1—13 | 
