No. 2. — Reports on the Results of Dredging, under the Supervision 

 of Alexander Agassiz, in the Gulf of Mexico, and in the Carib- 

 bean Sea, 1877-79, bg the United States Coast Survey Steamer 

 " Blake," Lieutenant-Commander C. D. Sigsbee, U. S. K, and 

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



(Published by permission of Carlile P. Patterson, Supt. U. S. Coast and Geodetic 



Survey.) 



XV. 



Preliminary Report on the Mollusca, by W. H. Dall. 



It has seemed desirable to those directing the pubHcations on these 

 materials, in order to secure proper recognition to those engaged in the 

 sounding and dredging work, that the description of the many new forms 

 contained in their collections be not longer delayed. Later laborers in 

 the same field have already, to some extent, duplicated the materials, 

 and this may be expected to go on in increasing ratio. I have, there- 

 fore, endeavored to give recognizable descriptions of those forms which 

 seemed to be new, reserving for further treatment the species on which 

 some doubt existed, or which from their habitat and appearance seemed 

 likely to belong more properly to the fauna of moderate depths. These 

 descriptions are only preliminary to the work in which they shall be 

 properly figured, without which, indeed, species of mollusks can hardly 

 be said to have been wholly published, especially in these days of refine- 

 ment in specific differentiation. 



The materials here described do not include collections obtained 

 by Professor Agassiz and Commander J. R. Bartlett, U. S. N., on the 

 "Blake," in the season of 1878-79, but with very few exceptions form 

 part of the mollusca gathered by the party on the "Blake," in 1877-78, 

 under Professor Agassiz's supervision, while the vessel was commanded 

 by Lieut.-Com. C. D. Sigsbee. The later collections, containing many 

 forms of great beauty, have not yet been administered upon, owing to 

 the limited leisure of the writer, and his absence on official duties. 



VOL. IX. — NO. 2. 3 



