64 BULLETIN OF THE BUREAU OF FISHERIES. 
tive species comprised in our local benthos. In many cases, however, highly instructive 
data have been obtained regarding forms of less frequent occurrence. Such have been 
referred to in the text. ' 
Records entered as doubtful have been excluded in plotting the distribution charts. 
In the charts for the shell-bearing mollusks and echinoderms, and for the coral A strangia, 
it will be found that the stars are in many cases surrounded by circles. The circle in 
each case indicates that one or more /1ving specimens were recorded from the station in 
question; absence of the circle implies either that the records indicate the presence of 
dead shells only, or that no statement has been made on the subject. 
3. THE FAUNA CONSIDERED ACCORDING TO REGIONS AND HABITATS. 
Many of the species encountered during our dredging operations were found to 
have a practically unrestricted distribution within the waters explored. In the case 
of many other species, their distribution was found to be definitely restricted, i. e., 
they were adapted to particular temperatures or to particular kinds of bottom. These 
various types of distribution will be discussed at some length in relation to particular 
species which serve to illustrate them, and many cases are portrayed graphically by 
means of charts. But it is likewise important that a list of the more prevalent species 
should be presented synoptically for each subregion of our chart and for each variety of 
habitat. With this in view the stations were tabulated in various ways, according to 
the type of bottom or the like; and for each of these groups lists were prepared 
comprising all of those species which were taken at one-fourth or more of the stations 
in question. We believe that lists thus restricted may be regarded as comprising 
only such species as are truly representative of these various bottoms. It must be 
conceded, however, that many of the less common forms which do not appear in the 
lists at all may be highly characteristic of one or another group of stations, and may, 
indeed, be limited to these. 
Preceding the lists for particular waters or particular types of bottom we present a 
table comprising those species which were taken at one-fourth or more of the total 
number of dredging stations of the Survey, i. e., at 115 or more of the regular stations.? 
It is believed that such a list conveys a good idea of the prevailing benthic fauna of our 
local waters, so far as we can speak of any single prevailing fauna where the conditions 
differ so widely. This list will perhaps render possible the detection of future changes in 
the relative abundance of certain species. 
a At first only those species were listed which were present at half or more of a given group of stations, but it was found that 
all of the resulting lists were very brief, and that they omitted many highly characteristic forms. 
b None of the supplementary stations, except the ‘‘bis”’ stations of 1904, have been considered in the present computations. 
The inclusion of the r909 records would doubtless change the complexion of these tables somewhat, though not, we believe, very 
materially. 
