No. 6. — Reports on the Dredging Operations off the West Coast of 
Central America to the Galapagos, to the West Coast of Mea- 
ico, and in the Gulf of California, in charge of ALEXANDER 
AGASSIZ, carried on by the U. S. Fish Commission Steamer 
“ Albatross” during 1891, Lieut. COMMANDER Z. L, TANNER, 
U. 5. N., Commanding, XXXV III. 
AND 
Reports on the Scientific Results of the Expedition to the Eastern 
Tropical Pacific in charge of ALEXANDER AGASSIZ, by the 
U. S. Fish Commission Steamer “ Albatross,” from October, 
1904, to March, 1905, Ligur. COMMANDER L. M. GARRETT, 
J. S. N., Commanding, XIV. 
Reports on the Mollusca and Brachiopoda. 
By WırLıam HEALEY DALL. 
Introduction. 
Tun following report includes in the material treated of, first, the 
Mollusca and Brachiopoda collected by the U. S. S. “ Albatross ” during 
the cruise of February to April, 1891, under the direction of Dr. 
Agassiz ; and, secondly, further material obtained during the voyage of 
1904-5, under the same auspices. 
At the suggestion of Dr. Agassiz, the molluscan material of the last 
Voyage having proved small in amount though most interesting in 
quality, the report was extended to cover both voyages, and for uus 
pleteness’ sake I have added a few species obtained in the same region by 
the * Albatross " during 1888, while on her way from the Atlantic to Cali- 
fornia, and which had remained without being worked up, having came 
into my custody after my report on the voyage of 1887-8 had been 
printed. . Tho few deep-water forms, a8 well as the shore and reef shells 
obtained during the Expedition to the Tropical Pacific, August, 1899, to 
March, 1900, are also included. 
