72 



BULLETIN OF THE BUREAU OF FISHERIES. 



Cirripedia: 



Balanus ebumeus (46). 

 Amphipoda: 



Ptilocheirus pinguis (41). 



Unciola irrorata (32). 

 Dec.\poda: 



Crago scptemspinosus (50). 



Pagurus longicaqjus (83). 



Pagurus annulipcs (44). 



Libinia caiarginata (57). 



Cancer irroratus (43). 



Neopanope texana saj'i (43). 

 PelEcypoda: 



Anomia simplex (74). 



Pecten gibbus borealis (57). 



Area transversa (78). 



Nucula proxima (74). 



Yoldia limatula (66). 



Crassinella mactracea (29). 



Cardium pinnnlatura (79). 



Lsevicardium mortoni (45). 



PELECYPODA — Continued. 



Venus mercenaria (52). 



Callocardia morrhuana (80). 



Tellina tenera (63). 



Macoma tenta (30). 



Ensis directus (64). 



Spisula solidissima (29). 



Mulinia lateralis (60). 



Clidiophora gouldiana (80). 

 Gastropoda: 



Busycon canaliculatum (43). 



Tritia trivittata (108). 



Anachis avara (67). 



Astyris lunata (48). 



Eupleura caudata (48). 



Urosalpinx cinereus (29). 



Littorina litorea, shells only (48). 



Crepidula fornicata (84). 



Crepidula plana (74). 



Polynices duplicata (35). 



Polynices triseriata (41). 



Of the 50 species comprised in the above list only two "are absent from that repre- 

 senting the prevailing species dredged by the Fish Hawk in Buzzards Bay; while only 

 7 species in the latter list are lacking from that for the muddy bottoms. The two groups 

 of species are thus not far from identical. On the other hand, 13 of those in the list for 

 muddy bottoms do not appear in either table for Vineyard Sound. Thirty-three of the 

 species (66 per cent) are common to the list for sandy bottoms, while 34 species (68 per 

 cent) are common to that for bottoms of gravel and stones. 



Comparing the lists for the three types of bottom, we find 13 species which appear 

 only in that for bottoms of stones and gravel, an equal number which appear only in 

 the list for niuddy bottoms, while 6 are peculiar to the list for sandy bottoms. Of the 13 

 prevalent mud-dwelling forms, all but i are annelids or mollusks. Of the 13 species 

 peculiar to the list for gravelly and stony bottoms, 3 are hydroids and 3 are ascidians, the 

 remainder being distributed through various phyla. The number of forms -Nyhich are 

 restricted to our list of prevalent species for bottoms of pure sand (free from mud on 

 the one hand, and from stones and gravel on the other) is a very short one. This is due 

 to the fact that the great majority of sand-dwelling species are not deterred by the pres- 

 ence of a certain proportion of stones and gravel, while many of them are equally at 

 home in sand which is somewhat muddy. In our classification, however, such bottoms 

 have been included under "gravel and stones" and "mud," respectively. At least two 

 of the species listed are, nevertheless, pretty definitely restricted to bottoms of pure 

 sand. These are the "lady crab" (pvalipes ocellatus) and the "sand dollar" (Echina- 

 rachnius parma). 



In any consideration of such tables as the foregoing, it must be borne in mind that 

 the fact of a species being restricted to one or another of the tables does not imply that 

 it is absent from the other types of bottom, or subdivisions of the region. Indeed, it 



<■ These two are contained in the Pkalarope Buzzards Bay list. 



