21 



supported by a narrow process, •whicli is about twice as deep as the 

 width of" the area, becoming somewhat pointed at the ends. Poral 

 plates numerous, situated obliquely to the direction of the area ; median 

 furrow distinct ; outer margins of the area very narrow. Interradial 

 plates and summit openings unknown. 



Locality and position, in the upper division of the Burlington Lime- 

 stone, Burlington, Iowa. — Collections of Rev. W. H. Barris and Mr. 



Wachsmuth. 



MOLLUSCA. 



Gasteropoda. 

 Genus Porcellia Leveille. 



PORCELLIA OBLIQUINODA (n. s.) Shell broadly umbilicate, volutions 

 contiguous ; a row of numerous, moderately raised, oblique nodes 

 running along each side of the shell a little nearest the back, giving it 

 a somewhat angular appearance there, from which point the shell is 

 regularly rounded on the back, and sloping with a curve to the next 

 inner volution. A distinct linear depression runs along the back of 

 the shell. The oblique position of the nodes, and the direction of 

 some faint strise of growth, seem to indicate that the dorsal notch was 

 broadly V-shaped. Our specimen is a fine sandstone cast, preserving 

 about three volutions and the matrix of part of another ; the full num- 

 ber was probably four or five. 



From P. nodosa Hall and P. crassinoda White and Whitfield, 

 the only other described species of this genus known to us in the 

 American rocks, it differs in the shape, size, and number of the 

 nodes, and the general proportions of the shell. 



Locality and position, in the sandstone of the Chemung beds at 

 Burlington, Iowa. 



Genus Bellerophon Montfort. 



Bellerophon panneus (n. s.) Shell subglobose, gradually expand- 

 ing, except at the lateral margins, where it expands abruptly ; transverse 

 section of the volution opposite the aperture an irregular ellipse ; um- 

 bilici narrow and deep, which, when not filled with the imbedding 

 material, display the rounded sides of the volutions, which are three or 

 more in number. The back of the shell is somewhat flattened, and 

 has a central longitudinal elevation, which becomes a distinct carina 

 at the front; surface marked by strong, irregular, undulating lines of 

 growth, becoming very rough towards the front margin. 



Locality and position, in the Chemung beds, at Burlington, Iowa. 



Bellerophon scriptiferus (n. s.) Body of shell rather small ; 

 volutions few, rounded, closely coiled; cross section elliptical; umbilici 

 small, rather deep ; last volution extremely expanded into a broad sub- 

 heart-shaped disc, the back margin not reaching quite so far back as the 



