161 



The prominent toothlike apophyses of these shells, render their 

 position among the genera of Naiades, as now received, somewhat 

 equivocal ; uniting, as they do, Alasmodon and Anodon ; and they 

 strengthen the idea entertained by many, that the modifications in 

 the number, position, or absence of teeth, according to which the 

 genera are now founded, are so gradual as to authorize us to regard 

 them as merely sub-genera of one grand genus. Should this view 

 be adopted, and to it Dr. G. is much inclined, he believes that an- 

 other subgeneric group might be instituted, equally as characteristic 

 as any now received ; and proposes as follows : 



Subgenus Pseudodon. Hinge margin with a tooth-like apophysis 

 on each valve, the surface of which is not fractured , but smoothly cov- 

 ered with enamel, fitting into corresponding undulations in the oppo- 

 site valve, that on the right valve closing in front of that on the left. 



Anod. inoscularis would be the type of this group, and to it 

 would belong A. Salweniana, edentula, Steicartii and perhaps 

 some others. 



Dr. Gould read a letter lately received from Mr. McClel- 

 land, of Calcutta, acknowledging the notice of his election 

 to Corresponding membership. 



Mr. Emerson read portions of a letter from Hon. H. Bar- 

 nard, of Nantucket, accompanying specimens of the nut of 

 Laodoicea Seychella?*um, and also a mass of Resin which 

 "exudes from a tree very similar to our white pine. It 

 came from the west coast of Central America, and is used 

 for such purposes as we use our pitch pine." 



Dr. C. T. Jackson gave an abstract of Lieut. Fremont's 

 Report of his Exploring Expedition to the Rocky Mountains. 



The narrative abounds in incident, and the facts collected are 

 very interesting. The river Platte was traced to its sources in the 

 Rocky Mountains, the highest peak of which was ascertained to be 

 13,570 ft. above the sea. The rock formations are limestone and 

 sandstone to 109° west longitude, where they rest immediately 

 upon the granite. About 350 species of plants were collected. 



Dr. C. T. Jackson announced that he had recently made 

 a chemical analysis of the Pink Scapolite, of Bolton, in 

 which he had discovered oxide of Cerium, — to which the 

 mineral apparently owes its beautiful color. 



PROCEEDINGS B. S. N. H. 19 MAY, 1844. 



