1866.] 



79 



[Greenleaf. 



Omphalopelta versicolor. 

 Asterolampra Marylandlca. 



" Moronensis ? Grev. 



" Darwinii. " 



Asteromphalus arachne. 



" Brookei. 



" Shadboltianius. 



Odontodiscus sp. ? 



MELOSIRE^. 



Mastogonia sexangula. 



" actinoptychus. 

 Stephanogonia polygonia. 

 Melosira sulcata {= M. marina.) 

 Pyxidicula crux. 

 « ? 



Xanthiopyxis globosa. 



Xanthiopyxis oblonga. 



CH^TOCEREjE. 



Dicladia capreolus. 

 Chaetoceros ? 



COCCONEIDEiE. 



Cocconeis scutellum. 

 u ? 



NAVICULE^. 



Navicula californica. 



" bombus. 



" lyra. 

 PInnularia peregrina. 

 Pleurosigma validum. 

 Toxonidia Gregoriana Donk. 



Section of Microscopy. November 14, 1866. 



The Curator in the chair. Seventeen members present. 



Mr. R. C. Greenleaf read a paper on the Diatoms, and other 

 microscopic objects found in soundings from the Gulf of Mex- 

 ico, between Sand Key and El Moro, made by Henrj^ Mitch- 

 ell, Esq., of the United States Coast Sui-vey. 



Mr. Mitchell was engaged the last winter in making a survey in 

 the Gulf of Mexico, from Sand Key to El Moro, and kindly furnished 

 me the dredgings from some of the deepest soundings which he made. 

 These gatherings were cleaned by our associate member, Mr. Charles 

 G. Bush, in an admirable manner, separating the calcareous shells, or 

 Foraminifera, of microscopical proportions, found at these great 

 depths, from the still more minute sllicious forms, consisting of Poly- 

 cystina, Diatomacece, and sponge spicules. This renders the study far 

 more pleasant and satisfactory than having them placed together on 

 the same slide-. 



These gatherings are not rich in Diatoms, but many of the speci- 

 mens are very beautiful of their kind. I find some of the forms pub- 



