Reports on the Results of Dredging, under the Supervision of Alex- 

 ander Agassiz, in the Gulf of Mexico (1877-78) and in the 

 Caribbean Sea (1879-80), by the U. S. Coast Survey Steamer 

 "Blake" Lieut.-Commander C. D. Sigsbee, U. S. N., and Com- 

 mander J. E. Bartlett, U. S. N., Commanding. 



[Published by Permission of Caelile P. Patterson and J. E. Hilgard, Super- 

 intendents of the U. S. Coast and Geodetic Survey.] 



XXIX. 



Report on the Mollusca, by W. H. Dall. — Part II. Gastropoda and 



Scaphopoda. 



The reader of this Report, for various details as to its origin, progress, 

 and results, is referred to the introductory remarks prefixed to Part I. 

 (Bull. Mus. Comp. Zool, Vol. XII. No. 6, pp. 171-186.) His attention 

 is especially called to the remarks upon nomenclature (p. 175), and the 

 acknowledgments for indebtedness to other scientific men and their 

 publications. 



In the present portion of the Report, the material offered by the 

 Blake Collection has been materially supplemented by the southern 

 dredgings of the U. S. Fish Commission Steamer " Albatross," and other 

 material collected in the region and now in the National Museum. It 

 was the original intention of the writer to make this Report a summary 

 to date of deep-sea research and fannal exploration of the geographical 

 province extending from Brazil to Cape Hatteras. But the material 

 has been collected so rapidly, and the study of it leads to such unex- 

 pected conclusions, in many cases, that it has been impracticable to do 

 this for all the families. A general bathymetrical review may be at- 

 tempted later ; the present paper contains data for any one ambitious 

 to make the attempt at once, but the writer prefers to defer it until 

 the results of the later dredgings of the Fish Commission and of the 

 French expeditions are at hand, to be combined into a paper which shall 

 represent the latest information on the subject. 



However, in the following Report will be found in several instances a 

 complete though brief review of all the species of a group known to 



VOL. xviii. 1 



