Naviculacea.] infusorial animalcules. 321 



Genus Asteromphaltjs, (Ehr.) Tfookem. — Six umbilical rays, 

 straight; five marginal rays, the sixth obsolete. (1 -420th.) Antarctic 

 Ocean. 



A. JRossii. — Six inflected umbilical rays ; five marginal, the sixth 

 obsolete. (l-504th.) 



A. Buchii. — Seven straight umbilical rays ; six marginal, the 

 seventh obsolete. (1 -504th.) 



A. Beaumontii. — Seven inflected umbilical rays ; six marginal, the 

 seventh obsolete. Diameter l-648th. 



A. Humholdtii. — Eight straight umbilical, and seven marginal rays, 

 the eighth marginal obsolete. Diameter l-372nd. (P. 14, f. 34.) 



A. Cwvierii. — Nine umbilical straight rays, and eight marginal, the 

 ninth marginal wanting. Diameter 1 -392nd. Antarctic Sea. 



Genus Atjlacodiscus. — Lorica composed of two equal valves, 

 orbicidai' and unilocular (one celled), with apertures on each valve 

 near the margin ; very shortly tubular, and severally continued to 

 the centre by a distinct furrow (sulcus.) 



Aulacodisci are Eupodisci, furnished, in the place of pediform 

 tubules, with bands radiating fi-om the centre, and becoming con- 

 nected with the tubercles seated just within the margin, and having 

 the surface of their valves granular and not cellular. 



A. crux. — Testules rather convex ; margin finely radiated, forming 

 a rim around the cellular, granular disc ; twelve pearl-like granules 

 in l-1200th, and some rows of gi-anules radiating from the centre, 

 with four series representing a crucial suture, stronger near the 

 margin. Diameter 1-3 84th. Eichmond, Yii'ginia. 



Genus Auxiscus. — Lorica bivalve, cylindrical (or orbicular) mul- 

 tiplying by perfect self- division; two large (not tubular) apertures 

 on each surface of the disc laterally, which also is not curhose. 



This genus differs from Cerataulus, in wanting the cirrhose surface 

 of the lateral discs, as also the tubular apertures. 



A. cylindricus. — Cylindrical, with a plane orbicular disc on each 

 side, having a rim, and a central area figured by various radiating 

 lines ; Avith two opposite apertures, opening obliquely on the margin. 

 <l-576th to l-288th,) 



A. (?) gigas. — Margin of the sides tumid and perforated, sculp- 



