1 84 



BULLETIN OF THE BUREAU OF FISHERIES. 



and to what degree they are due to geographical isolation we can not say. The surface 

 temperature of the sea in the neighborhood of Plymouth is said to range from about 

 44° F. (February) to about 59 F. (August). (See Dickson, 1892, p. 276.) In this 

 respect the conditions are far different from those in Vineyard Sound, in which the 

 annual range of temperature is roughly from 30 F., or less, to 70°. On the other hand, 

 we know that broad expanses of ocean are effective barriers to distribution, even for 

 marine organisms. 



Although we have not undertaken the ambitious task of making extended com- 

 parisons between the Woods Hole fauna and the faunas of other sections of the Atlantic 

 coast, we have nevertheless been able to give some answer to the questions: (1) Have 

 the majority of our more representative species a range which is predominantly north- 

 ward or one which is predominantly southward ? (2) In how large a degree is Cape 

 Cod a barrier to distribution ? 



As stated above, we have considered for this purpose only those species which have 

 been taken at 10 or more of our dredging stations, and which, therefore, may be regarded 

 as those which are most truly representative of our local benthos. Of such species there 

 are 202, excluding 9 species of Protozoa. In the various sections of chapter iv these 

 species have been grouped according to their range upon our coast, and a synopsis of 

 these separate lists is presented in a table herewith. It may be repeated that a species 

 has been regarded as predominantly northward-ranging, whose range (in latitude) to 

 the northward on our coast is at least twice as great as its range to the southward. 

 A species has been regarded as southward-ranging which presents the converse type of 

 distribution. The column headed "Equal" refers to those species whose known range 

 in one direction does not greatly exceed the known range in the other direction; while 

 the doubtful column includes those concerning which our data are insufficient. In many 

 cases they have been found only in the immediate vicinity of Woods Hole. 





Predom- 

 inantly 

 northern. 



Predom- 

 inantly 

 southern. 



Equal. 



Doubt- 

 ful. 



Total. 



Known 

 to occur 

 north of 

 Cape Cod. 



Known 

 to occur 

 south of 

 Woods 



Hole 

 region.' 1 





6 



3 



5 



3 



1 





3 

 13 



7 

 30 



19 

 3 



13 

 2 



68 

 8 



13 



n 

 12 

 6 

 13 



1 

 8 

 1 

 8 

 1 



SO 

 3 



13 







6 



1 















2 







j 







5 



43 



5 





j 





7 





7 







3 







2 









1 

 1 



t 





16 



8 



67 





S 





» 



6 











46 



101 



31 



24 



202 



130 









a This criterion has not been applied to those cases in which it is definitely known that the extreme southern records relate 

 only to great depths. 



b I/mg Island Sound has not been regarded as south of the Woods Hole region. Had it been so considered, the figures in 

 this column would have been materially increased. 



