237] J* A. Gardner 39 



stricted. This is especially true in certain families. In a 

 recent zoogeographic study of the West Coast Pyrammidelli- 

 dae 10 faunal zones were differentiated. 2 The three most 

 populous were the Oregonic with 70 species, the Californic 

 with 164 and the Mazatlanic with 75. However, only 11 

 species common to the Oregonic and Californic were recog- 

 nized and only 2 common to the Californic and Mazatlanic. 

 No refined study such as this has ever been made upon any 

 of the East Coast molluscs, but when it is done the number 

 of species will doubtless be greatly increased and their ranges 

 greatly diminished. The fossil forms can then be interpreted 

 in terms of the Eecent with an accuracy and a detail far in 

 advance of anything that is possible at present. The knowl- 

 edge of the Tertiary ecology may approximate the Recent 

 but it can never go beyond it. 



2. The limited number of dredging records. 



Not only are the stations relatively few in number but 

 they are so grouped that there are long stretches which have 

 not yet been touched. The attempt has been made, however, 

 to cover the critical areas, such as that of the Florida coast, 

 Hatteras and Woods Hole. The New England fauna is well 

 known in a general way and extensive collections have been 

 made through the 'Gulf and the West Indies by the Blake 

 and the Albatross. A very short but significant report is that 

 of Bartsch and Henderson upon a two days' collecting trip 

 off Chincoteague Island on the Virginia coast for the pur- 

 pose of determining the extent of overlap of the southern 

 fauna. 3 The latest of the larger reports, that upon the 

 Woods Hole region is by far the most satisfactory excepting 

 that it covers an area so restricted and so little diversified. 

 The arrangement, however, is excellent for an ecologic study, 

 the dead shells are isolated from the living and the young 



2 Bartsch, P., 1912, Proc. u. S. National Museum, vol. 42, p. 299. 



3 Bartsch and Henderson, 1914, Proc. U. 8. Nat. Mus., vol. 47, pp. 

 411-421. 



