AXEL A. OLSSON 



Percentage of known species ranging from Gulf of 

 California to Ecuador or to Peru 



Exclusive of the cephalopods, nudibranchs, sea hares and the pteropods, 

 the remaining groups of Panamic-Pacific mollusks have been conservatively 

 estimated at about 2200 species. This estimate compiled some time ago is 

 as follows: 



Gastropoda -....„ „ 1662 species 



Pelecypoda „ 496 species 



Scaphopoda — 14 species 



Amphineura ....„ _ 27 species 



Total 2199 species 



Gastropoda 



As would be expected, this class of the Mollusca contains the largest 

 number of species, about three times all others combined. The number esti- 

 mated above will no doubt be increased when such large families as the 

 Turridae, Columbellidae, Caecidae, and Pyramidellidae are fully known. 

 Other families may be reduced in the number of valid species attributed 

 to them after revisional studies are made. 



The gastropods include some of the finest and most interesting of 

 Panamic mollusks. The Cancellariidae are well represented (about 33 

 species) with such fine species as C. (Pyruclia) solida, probably the largest 



