EAST AMERICAN SCAPHOPOD MOLLUSKS. 15 



2. Of southern shallow and moderate depth forms but one (C. 

 agassizii) passes Hatteras, and this along the Gulf Stream edge. 



3. Many deep-water species have a very extensive southern range, 

 but even in their cases Hatteras seems to form a recognizable barrier 

 against northern migration. An exception is noted in B. meridionale, 

 which, considered as a superspecies, extends from Brazil to Georges 

 Banks, but in a least recorded depth of about 700 fathoms. 



4. The majority of species enumerated belong to what might be 

 called in broad terms an Antillean fauna. They are usually noted 

 from more than one Antillean locality, and a large proportion of them 

 appear along the Florida keys and the sweep of the Gulf Stream. 

 Those Antillean species not found in the Florida Straits are of very 

 restricted local distribution or belong to the greater depth zones. 



5. A certain number of Florida Key species are not of Antillean 

 range, but appear occasionally in the Gulf of Mexico and have a 

 range northerly withm the Gulf Stream influence to Hatteras. These 

 seem to constitute a more strictly Floridian element. 



6. A few species (D. texasianum, 'pseudoliexagonum, disparile, seri- 

 catum,, liodon, C. aco7npsus, watsoni, and 'providensis) seem to indicate 

 a scheme of distribution which includes the mainland coast from 

 Brazil to West Florida and the Carolinas, and excludes all the Antilles 

 save Barbados; nor are they to be found m the Gulf Stream. Just 

 how far such a faunal element may be differentiated is now unsafe 

 to say in view of our imperfect knowledge of the area involved. 

 There is a significance, however, in the present record, for it will also 

 be noted that all our Brazilian records are only repeated in the Bar- 

 badian region, along the mainland shores and in the Gulf of Mexico, 

 but not in the broad Antillean region, nor in the Gulf Stream. I 

 exclude from these only the abyssal ocean floor species. 



7. A false note is touched in an 11-fathom station off Rio de la 

 Plata quoted four times in our table, and in each instance for deep- 

 water species of other stations. I feel quite sure that some error 

 has been made in recording this station (No. 2714) by the United 

 States Fish Commission. 



In conclusion, then, I would say we have to deal with two well- 

 defined and clearly marked faunas — first, a northern cold-water 

 group of close northern Europe affiliations, and extending from the 

 New England region and its outer banks to Hatteras; second, an 

 Antillean assemblage of very extensive range from Brazil to Hatteras, 

 with the dominating influence of the currents entering the Caribbean 

 from the Atlantic and tlebouching from the Gulf as the Gulf Stream 

 as the main distributional force. Within this great area are likely 

 certain well-marked subfaunal areas, two of which are recognizable 

 from our table. One of these is a mainland coastal faunula and the 

 other a Floridian element which includes the area bordering the inner 

 edge of the Gulf Stream from lower Florida to Cape Lookout or 

 Hatteras. 



