Naoiculacea."] INFUSORIAL animalcules. 435 



PrxiDicuLA major (Kiitz.) — Largo, forming a bivalve, elliptic box; 

 valves (patcllse, Ehr.) very convex, conical, regularly punctate. 

 Diameter l-420tli. Virginia and Normandy. 



P. Adriatica. — Adnate, sessile, of middle size, bivalve ; valves con- 

 vex, mostly beraisplierical, and quite smooth. Diameter l-600tli. 

 On Cladophora, Trieste. (P. 16, f. 33.) 



P. minor, = P. opercidata (Bailey). — Fossil. A doubtful species, 

 and probably a detached fi-ustule of a Melosira, — Gallionelh. 



P. (?) comprcssa (Bailey.) — Elliptical, bivalve ; valves separated 

 by a plane passing through the longer axis, slightly convex, and 

 "with transverse rows of dots. St. Augustine. 



Sub-genus Drciro pyxis (Ehr.) — Those subglobose or turgid forms 

 of the genus Pt/xklkida which are characterised by a cellular con- 

 striction of the valves, are clearly and readily distinguished from 

 those which have a single and continuous siliceous investment, or 

 are furnished with appendages. I have therefore thought it right 

 to separate the former cellular species from the others, and to con- 

 stitute them a distinct sub-genus of Pyxidicula, under the appellation 

 of Bicttjopyxis. 



" Erom the same genus — Pyxidicula — so abundant in forms, I have 

 abstracted other distinguishable species, and have created the genera 

 Mastogonia, and Sfephanogonia, and the sub-genera Steplianopyxis and 

 X.ant'kiopjxis.^'' 



D. cruciata = Pyxidicula cruciata (1843). Eesemblcs generally 

 D. JHellenica, but differs in size, and has larger areoloo on its surface. 

 D. Hellenica. — Ovate, oblong ; valves urceolate ; surface with cells 

 in longitudinal rows. Length 1 -720th. Eossil in Greek marl. 



D. cylindnts = Pyxidicula cylindrus. — Cylindrical, three times 

 longer than broad ; surface of valves (patellae) with obscure rows of 

 cells ; apices rather tapering. Diameter l-960th. Maryland. 



D. Lens — Pyxidicula Lens. — Lenticular and flattened laterally; 

 surface of valves cellular. Diameter l-63Gth. Yirginia. 



D. Scaralaus. — Oblong, with unequal valves ; when viewed late- 

 rally recalling the figure of the Scaraboeus. Diameter 1-G48tli. 

 CeUs 14 in 1-1 150th. Eossil, Virginia. 



Sub-genus SxEriiANorYxis.— Includes those turgid, bivalve, sub- 



