OF THE FAMILY BACILLARIA. 135 



PYXIDICULA. 



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

 {may be compared to a Gaillonella tvit/i perfect spontaneous clivi- 

 sion or ivithout division.) 



1. Pyxidicida operculata. (PL 11, fig. 1 and la.) Body spherical, 

 divisible into two hemispheres, carapace hyaline, internal organs 

 greenish yellow, Y20 to one forty-eighth of a line. 



I have seen hemispheres, probably derived from this species, 

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



2. Pyxidicida glohata. This name has been given to globnlar 

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

 found in Pritchard's Hist. Infusoria, pi. 12, figs, 506 to 509. It is now 

 suspected that these bodies are the gemmules of sponges, as the 

 ramified tubes of sponge ara often found preserved in the same 

 pieces of flint. 



3. Pyxidicida? (PI. II, fig 2, a, b.) The spheroidal bodies, repre- 

 sented by these figures, occur in the tertiary infusorial stratum 

 discovered by Prof W. B. Rogers in Virginia. Of the real nature 

 of these bodies I am quite uncertain ; they agree however with 

 Pyxidicula, in separating into two hemispherical portions. The 

 surface is beautifully marked with rows of circular or hexagonal spots 

 or cells, resembling those on the beautiful species of Coscinodiscus 

 which accompany these bodies in the same deposit. 



GAILLONELLA. 



Free, carapace simple, bivalve (siliceoKs), form cylindrical, 

 globular or discoid, producing chains [long articulated cylinders] 

 by imperfect spontaneous division. 



1. Gaillonella moniliformis. (PI. II, fig. 3.) Corpuscles smooth, 

 cylindrical, short, conical at the sides and truncate, form octangular [?] 

 circular when seen endwise, ovaries green, one seventy-second of a 

 line. Ehr. Meloseria moniliformis, Ktz., Linn., 1833, PI. 17, fig. 71. 

 M. nummuloides, Gh'ev., in Brit. Flora, V. p. 401. 



This very beautiful species grows only in salt or brackish water, 

 and occurs in great abundance in various places in the United 

 States, I first noticed it several years ago, among specimens 

 of Alg(e from Providence, R. I. I subsequently found it almost 



