88 Sketch of the Infusoria of the family Badllaria. 



Art. X. — A Sketch of the hifusoria, of the family Badllaria, 

 with some account of the most interestijig species which have 

 been found in a recent or fossil state in the United States ; by 

 J. W. Bailky, Professor of Chemistry, Mineralogy, and Geol- 

 ogy, in the United States Military Academy. 



Part II * 



Having given in the preceding part of this memoir, some ac- 

 count of those Baciilariae which belong to the section Desmidi- 

 acea, I continue the subject in the present part, by describing the 

 Baciilariae of the section Naviculacea. 



As all the species referred to this section have siliceous cov- 

 erings, they often occur in a fossil state, and hence their study is 

 of peculiar interest to the geologist. In beauty of form and ele- 

 gance of structure, they will bear comparison with almost any class 

 of organized beings. 



Sect. II. NAYICULACEA. 



PrXIDICULA. 



Free, carapace simple, bivalve (siliceous) separate, globular, 

 (may be coinpared to a Gailloriella with perfect spontaneous divi- 

 sion or without division.) 



1. Pyxidicula operculata. (PI. 2, fig. 1 and 1 a.) Body spherical, 

 divisible into two hemispheres, carapace hyaline, internal organs green- 

 ish yellow, Y^^ to -^-^ line. 



I have seen hemispheres, probably derived from this species, 

 among fossil infusoria from Manchester, Mass., &c. 



2. Pyxidicula gloiata. This name has been given to globular bodies 

 found in flint. Beautiful figures of them by Bauer, will be found in 

 Pritchard's Hist. Infusoi'ia, pi. 12, figs. 506 to 509. It is now suspect- 

 ed that these bodies are the gemmules of sponges, as the ramified tubes 

 of sponge are often found preserved in the same pieces of flint. 



3. Pyxidicula 1 (PI. 2, fig. 2, a, b.) The spheroidal bodies repre- 

 sented by these figures, occur in the tertiary infusorial stratum discovered 



* Since ihe second part of this memoir w.is ready for tlie press, I have received 

 Pritchard's beautiful work entitled " History of Infusoria living and fossil." J have 

 gladly availed myself of the onportunity to introduce here many of the novel 

 facts which it contains. Many of these facts will be given in the form of notes, 

 as time does not now allow me to incorporate them in this sketch in any other 

 form . 



