104 BULLETIN OF THE BUREAU OF FISHERIES. 



attach themselves to various other fixed organisms, or directly to piles or stones. Flus- 

 trella hispida forms a thick matting over the rockweed along shore, and several species 

 may be found upon active living animals, such as crabs. One, indeed, makes its home 

 in the gill chamber of the blue crab (Callinectes sapidus). Various minute Bryozoa may 

 readily be mistaken for hydroids, or may be overlooked altogether. Thus there is little 

 doubt that many such forms escaped the collectors entirely during the earlier dredging 

 work of the survey. With some few exceptions, the incrusting species are the ones 

 which figure most prominently in the dredging records, colonies of this sort seldom being 

 absent from stones or shells. Owing to the superficial similarity of several quite dis- 

 tinct species of incrusting Bryozoa, it was our practice throughout the dredging work to 

 save for preservation samples of even the commonest species from every dredge haul in 

 which they occurred. Only three species of Bryozoa (Bugula turrita, Crista eburnea, 

 and Cellepora americana) were regularly identified by the collectors in the field, and there 

 seems to be little probability that these were confused with any less familiar forms. 

 All other species, so far as detected, were preserved for future examination. These were 

 later identified by Dr. Osburn, who is likewise responsible for the classification here 

 adopted. 



Charts (27-46) have been prepared showing the distribution of those species which 

 were recorded from 10 or more of the dredging stations." Two of these species, Lepralia 

 americana and L. pallasiana, were confused in the earlier dredging records to such an 

 extent that it has been thought best to plot their combined distributions upon a single 

 chart. Thus there are only 20 charts for these 2 1 species. 



Less of general interest is to be gathered from the local distribution of the Bryozoa 

 than from that of many other groups which we have considered. Only two distinct 

 types of distribution are to be found among those forms which have been dredged with 

 any frequency in local waters. We have (1) species whose distribution is general, or 

 without any definite restrictions throughout Vineyard Sound and Buzzards Bay; and 

 (2) species found wholly, or at least predominantly, in Vineyard Sound. Not a single 

 species has been found which appears to be restricted in any degree to the Bay. Thus 

 the phylum has a considerably greater representation in the Sound than in the Bay. 

 The average number of species taken per dredge haul 6 may be tabulated as follows : 



Vineyard Sound: 



Fish Hawk stations 3.4 



Phalarope stations 3. o 



Buzzards Bay: 



Fish Hawk stations 2.7 



Phalarope stations 2.0 



The average number of species for the Crab Ledge stations would doubtless greatly 

 exceed any of these figures, but unfortunately the data are not available. 



It is highly probable that the character of the bottom has been the chief factor in 

 determining the results here tabulated, just as in the case of the Hydrozoa. Reference 

 to the table on page 79 shows that the average number of species per dredge haul for 



o Including the supplementary stations of 1906-1909, for the same reason as already stated in the ease of the Foraminifera 

 and ceelenterates. 



b Based upon the original stations only. Were the supplementary dredgings to be considered in this computation, it is likely 

 that the figures for Buzzards Bay would be somewhat greater, though it is quite improbable that they would equal those for 

 Vineyard Sound. 



