No. 6.— Reports on the Results of Dredging, under the Supervision 
of ALEXANDER 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. SicsBEE, U. 8. N., and Com- 
MANDER J. R. Bartuert, U. 8. N., Commanding. 
(Published by permission of CarLiLe P. Parrerson and J. E. Hitearp, Superin- 
tendents of the U. S. Coast and Geodetic Survey.) 
XXIX. 
Report on the Mollusca, by W. H. Datu. — Part I. Brachiopoda and 
Pelecypoda. 
In 1878, the mollusks of the ‘‘ Blake” were intrusted to me for exami- 
nation and report, and a Preliminary Note upon them appeared in August 
of that year (Bull. Mus. Comp. Zodl., Vol. V. No. 6, pp. 60-62). 
The following season a second instalment was received, and, in Feb- 
ruary, 1880, after a cursory examination of the material, I was enabled 
to furnish Prof. Agassiz with a short résumé of the general conclusions 
which seemed to result from the data obtained by that examination 
(Bull. M. C. Z., Vol. VI. No. 3, pp. 85-93). 
My time during ordinary working hours being absorbed by official 
duties, and the entire period from February, 1880, to January, 1881, 
being occupied by field-work on the Pacific coast, progress has neces- 
sarily been slow; the more so, as nearly all the material consists of 
specimens so small as to require reiterated scrutiny under a glass to 
determine their characters. To separate and label the specimens con- 
tained in nearly two hundred different lots, to select specimens for 
figuring and to scrutinize and revise the drawings, to search the lit- 
erature relating to mollusks for the scattered data in relation to such 
as are native to the region in question, and to accurately describe such 
species as seemed to be new, bas been the task before me, to be carried 
out in the scanty leisure afforded by such evenings and holidays as were 
not necessarily otherwise employed. The delay in completing the work, 
it will be seen, has been inevitable under the circumstances, and my 
thanks are due to Prof. Agassiz, and others interested, for the patience 
with which they have kept these circumstances in mind. 
VOL. XII. — NO. 6. zk 
