112 BULLETIN OF THE BUREAU OF FISHERIES. 



however, been retained in the list of stations for this starfish, as given in our catalogue, 

 though their doubtful nature has been indicated. Supplementary dredgings were 

 made in Buzzards Bay during two subsequent seasons, partly for the purpose of 

 testing this feature in the distribution of Asterias vulgaris. Out of a total of nearly 

 60 stations, starfishes of this genus were recorded for 1 1 . These were in all cases 

 assignable to Asterias forbesi, with the exception of a few small specimens of A. 

 vulgaris taken at two stations situated near the island shores and not far from the 

 mouth of the Bay. Accordingly we regard the occurrence of the latter species in the 

 interior portions of Buzzards Bay as being extremely doubtful. 



(2) Doubt has been cast upon our earliest field identifications of the ophiuroids. 

 For this reason, it has been regarded as fairer to bring together the records for the first 

 year, except such as are based upon authoritative determinations, under the heading 

 "ophiuroids unidentified." Such specimens were probably in most cases referable to the 

 species Amphipholis squamata. 



Distribution charts have been plotted for seven species of echinoderms (charts 

 47 to SS)-" It will be seen at a glance that only two of these species {Asterias forbesi and 

 Arbacia piinctulata) were encountered with any frequency in Buzzards Bay, while of 

 these two the former alone was generally distributed throughout the central portions 

 of the Bay. Arbacia and certain other species (notably Henricia) were found to be 

 largely restricted, in Buzzards Bay, to the immediate neighborhood of land. For these 

 facts, as for similar ones already discussed in our treatment of other groups, we believe 

 that the character of the bottom is chiefly responsible. Most of our commoner local 

 echinoderms prefer bottoms of gravel or sand to ones of mud. To this statement, it is 

 true, exceptions are offered by some of the holothurians and ophiuroids. 



From the table on page 79 it will be seen that the average number of species of 

 echinoderms per dredge haul, taken upon bottoms of gravel and stones, is 2.2; that for 

 sandy bottoms being 2.0, and that for muddy bottoms being only 1.2. The different 

 classes, however, do not agree in these preferences. The figures both for holothuroidea 

 and ophiuroidea are greatest for muddy bottoms; but, owing to their infrequent occur- 

 rence in the dredge hauls, they do not seriously affect these averages. 



The relative wealth of the echinoderm fauna upon different types of bottom is 

 shown in another way by an enumeration of the species which were taken in one-fourth 

 or more of the dredge hauls made upon bottoms of each type (p. 70, 71). In the list 

 for sandy bottoms are comprised 2 asteroids and 2 echinoids; in that for gravelly and 

 stony bottoms, 2 asteroids and i echinoid; in that for muddy bottoms, a single asteroid 

 and no echinoids. Similarly, 3 asteroids and 2 echinoids appear in the list of species 

 (p. 65) taken at one-fourth or more of the Fish Hawk stations in Vineyard Sound, while 

 only I asteroid and no echinoids appear in the corresponding list for Buzzards Bay. The 

 lists for the Phalarope stations in the two bodies of water do not show as great differ- 

 ences, since the conditions in the "adlittoral" region are more nearly similar throughout, 

 but the preponderance is nevertheless somewhat in favor of Vineyard Sound. 



A species which is restricted more than any other to bottoms of pure sand * is the 

 "sand dollar," Echinarachnius parma. Character of the bottom, rather than tempera- 



a In the case of the charts for shell-bearing organisms, the occurrence of living specimens at a given station has been indicated 

 by a circle surrounding the star. Among the echinoderms this practice has been followed only in the case of the two sea urchins, 

 Arbacia and StrvnQytocenlrolus, these being the only ones which would be likely to leave behind enduring remains. It has 

 been assumed for these two that all the field records relate to living specimens unless the contrary is expressly stated. 



b The dead tests are of more general occurrence, owing probably to the fact that they may be drifted by tidal currents. 



