208 BULLETIN OF THE BUREAU OF FISHERIES. 



Crab Ledge differs noticeably from the Sound and Bay. The depth is in general a 

 little greater (14 to 20 fathoms), but this is not sufficient to have any particular value. 

 The temperature in midsummer is noticeably colder. Records taken on the same day 

 (Aug. 12, 1909) by Dr. Cole and myself showed a mean bottom temperature of 47.2° F. 

 at ijyi fathoms on Crab Ledge, and 69.5° F. at 12 fathoms off West Chop, in the eastern 

 end of Vineyard Sound. The much lower temperature of Crab Ledge, Great Round 

 Shoal, and Nantucket Shoals, due no doubt to their proximity to the deeper water of 

 the open ocean, permits a considerable number of northern species to live on these 

 shoals which are not represented in Vineyard Sound and Buzzards Bay. Crab Ledge 

 in particular is of interest in yielding a number of species supposed to be limited in their 

 distribution to northern waters and which have not hitherto been reported south of 

 Canada. 



In comparing the distribution of species in the following pages I have made use of 

 the term "inner waters" to distinguish Buzzards Bay and Vineyard Sound from the 

 other stations which I have designated collectively as the "outer waters." 



In the outer waters there are found about 28 species not represented in the inner 

 waters. These are : 



Crisia crlbraria. 



Stomatopora diastoporoides. 



Tubulipora flabellaris. 



Tubulipora atlantica. 



Gemellaria loricata. 



Scruparia clavata. 



Caberea ellisii. 



Menipea temata. 



Cellularia peachii. 



Bugula murrayana. 



Bugula cticullifera (B. cucullata Verrill non Busk). 



Membranipora arctica. 



llembranipora cymbEeformis. 



Membranipora unicornis. 



Cribrilina annulata. 



Porina tubulosa. 



Schizoporella sinuosa. 



Schizoporella auriculata. 



Cellepora canaliculata. 



Mucronella venUicosa. 



Rhamphostomella costata. 



Porella acutirostris. 



Porella proboscidea. 



Porella concinna. 



Smittia porifera. 



Alcyonidium parasitictun. 



