FAUNA AND FLORA OF THE SEA BOTTOM. 1 233 



limits? In other words, do the majority of species have a range which extends 

 mainly to the northward along this coast, or do the majority have, on the whole, 

 a southward range; or is there no appreciable preponderance of one sort over 

 the other? Simple as these questions may seem, it is difficult to give an answer 

 that is at all satisfactory. The known range, as distinguished from the actual 

 range, of a species, is very frequently determined by historical accident. Thus 

 the Bay of Fundy, Massachusetts Bay, Woods Hole, New Haven, Charleston, 

 etc., frequently figure in our literature as limits of distribution, and this for 

 obvious reasons. Similarly, Cape Cod has taken a conspicuous place as a limit 

 of distribution in all the accounts of our Atlantic Coast fauna and flora. In 

 fact, it has been pretty generally assumed that Cape Cod forms a rather definite 

 boundary between the fauna and flora inhabiting the regions above and below it. 

 This was urged by Gould" as early as 1840, and has been maintained by Dana, 

 Verrill, S. I. Smith, and others for the animal kingdom, and by Harvey and Far- 

 low for plants. The faunal region extending to the southward of this barrier 

 has been termed the Virginian, that to the northward the Acadian,'' Woods Hole 

 and the adjacent waters being assigned to the former. While it would be vain 

 to dispute the importance of the barrier formed by Cape Cod and the outlying 

 islands and shoals, together with the temperature conditions associated with 

 them, it seems probable that its significance has often been exaggerated, owing 

 to the historical prominence of this region of the coast in the annals of American 

 zoology and botany. Some facts are herewith offered in support of this opinion. 



Of the 202 species of animals which have been taken at 10 or more of our 

 dredging stations, and which, therefore, may be regarded as representative of 

 our local marine fauna, 100, or almost exactly 50 per cent, are reputed to have a 

 range on our coast which is predominantly southward. By this it is meant 

 that the extent of their known range to the southward is at least twice that of 

 their known range to the northward. On the other hand, 48 of the species (24 

 per cent) have a range which is predominantly northward, while 29 of them (14 

 per cent) have a range of approximately equal extent (so far as known) in both 

 directions. The remaining 25 species have been relegated to the doubtful 

 column, owing to the unsatisfactory nature of the data at our disposal; some 

 of these forms having been found only in the vicinity of Woods Hole. The 

 fact to be emphasized is that the ratio of southward-ranging species (as thus 

 defined) to northward-ranging species is approximately two to one, while about 

 14 per cent of them do not seem to be thus restricted in latitude. 



Viewing these 202 species in another way, it is to be noted that 129, or about 

 63 per cent of them, are known to have a range extending north of Cape Cod, 



a Boston Journal of Natural History, vol. III. 



6 See particularly Verrill, in Proceedings of the Boston Society of Natural History, vol. x, 1866, p. 

 333-357- 



