18 REPORT ON NATIONAL MUSEUM, 1886. 



and pearl formations, cameo shells, and sections showing the internal 

 structure of various large and ornamental species. A provisional dis- 

 play of the principal economic mollusks of North America has also been 

 made. Under the supervision of Dr. R. E. 0. Stearns, adjunct curator, 

 an exhibit of the edible mollusks from the Atlantic and Pacific, of or- 

 namental species from tropical seas, and of land and fresh-water spe- 

 cies, has been installed. There is no room at present for the exhibition 

 of the general collection. 



The work of the curator and his assistants has consisted chiefly in 

 the identification of specimens for teachers and others in various parts 

 of the United States; the identification and classification of the recent 

 or living mollusks of the Atlantic coast of North America, as well as 

 those of the Antillean-Caribbeau region ; and the arrangement of laud, 

 pond, and fluviatile gastropods, as well as the fresh-water Acephala, 

 for the purposes of comparison and investigation in the matter of geo- 

 graphical distribution and variation of species as related to and affected 

 by environmental conditions. 



Among the most important investigations in progress is that of Mr. 

 Dall upon the deep-sea mollusks and his studies upon the Quaternary 

 molluscan fauna of the United States; and the continuation of pre- 

 vious investigations by Dr. Stearns on the geographical distribution 

 of the laud and fresh- water mollusks of North America and the varia- 

 tion of the same, as related to and affected by the physical characters of 

 their environment. 



DEPARTMENT OF INSECTS. 



This department was organized three years ago, but little has hitherto 

 been attempted beyond the preservation of the collections; Dr. 0. V. 

 Riley, the honorary curator, having been without an aid. An assistant 

 curatorship, to wthich Mr. John B. Smith has been appointed, was estab- 

 lished at the beginning of this year, and additional accommodations in 

 the laboratory and exhibition hall have been provided, thus permitting 

 an important extension of the study and exhibition series. 



In October Dr. O. V. Riley formally presented to the Museum his ex- 

 tensive private collection of North American insects, containing over 

 115,000 pinned specimens, representing over 20,000 species. This col- 

 lection is the result of his labors in collecting and study for more than 

 twenty-five years. 



It is estimated that there are now at least 500,000 specimens in the 

 collection. 



