BIOLOGICAL SURVEY OF WOODS HOLE AND VICINITY. 119 



although we have encountered these tubes (or rather short segments of tubes) at 198 

 stations throughout Vineyard Sound and Buzzards Bay, we have not a single record 

 of having taken even the anterior portion of the worm itself in the course of our dredg- 

 ing. Our records for Ch<etopterus pergamentaceus, Clymenella lorquala, Melinna macu- 

 lata, and the two species of Pista likewise relate almost exclusively to tubes; although 

 the first two of these species, at least, may be readily collected by digging in shallow 

 water. It is highly probable also that some small and inconspicuous species were 

 pretty constantly lost or overlooked in the process of washing large quantities of mud 

 or sand, particularly as we were seldom assisted in the field by anyone having an ade- 

 quate knowledge of this group. 



Mistakes due to the actual confusion of one species with another in the field records 

 are probably particularly infrequent for the annelids, in as much as nearly all of the 

 specimens were reserved for identification by Dr. Moore. The one known case in which 

 a certain degree of confusion exists is that of the small tube-dwelling worms of the genus 

 Spirorbis. It was not at first realized that several species of closely similar appearance 

 existed within the limits of the region dredged, and for this reason it was not thought 

 necessary to save samples from every dredge haul. It has consequently been found 

 necessary to list a considerable proportion of our specimens merely as "Spirorbis sp. 

 undetermined;" and it has not seemed worth while to present the distribution charts 

 for any members of the genus, although at least one of these (S. lubceformis) is known 

 to have been taken at more than 10 stations. 



On the average, 4.3 species of Annulata were recorded for each of the Survey dredge 

 hauls. The species found to have the most general distribution was Hydroides dianthus, 

 which was taken at 223 of the 458 stations. Those encountered so frequently as to be 

 taken at one-fourth of the total number of stations were : 



Hydroides dianthus (223). 



Diopatra cuprea (198). 



Nereis pelagica (192). 



Harmothoe imbricata (189). 



Lepidonotus squamatus (165). 

 As might have been readily inferred from the habits of this group of organisms, the 

 character of the bottom was found to be the dominant influence in determining their dis- 

 tribution. Now, we have seen that the bottom of Buzzards Bay, as a whole, is muddy, 

 whereas most portions of Vineyard Sound, however much they differ in other respects, 

 agree in the scarcity of mud. Accordingly we find it possible to divide the majority of 

 the annelids from the Survey dredgings into predominantly Bay-dwelling and predom- 

 inantly Sound-dwelling forms. 



As judged by our dredging records, members of this phylum are encountered with 

 considerably greater frequency in Buzzards Bay than in Vineyard Sound. 6 The average 

 number of species taken per dredge haul for each body of water and for each vessel may 

 be tabulated as follows : 



Vineyard Sound: 



Fish Hawk stations 3.5 



Phalarope stations 4.6 



Buzzards Bay: 



Fish Hawk stations 6. 2 



Phalarope stations 4. 6 



o To obtain satisfactory results, portions of the bottom material should be covered with sea water and left standing in dishes 

 lor some hours. 



* This statement is in no way inconsistent with the fact that the total number of species recorded for the Sound as a whole 

 is considerably greater than that recorded for the Bay (p. 80). 



