236 Twenty-third Report ox the State Cabinet. 



order ; parasitic on and incrusting foreign bodies in tlie form of den- 

 dritic branches ; tubes less than one-fiftieth of an inch in diameter, 

 rugose throughout the entire length. Cells branching from the main 

 trunk at intervals of about one-fortieth of an inch in direct succession ; 

 the alternation with those on the opposite side gives a cell for every 

 eighth of an inch ; cell-apertures opening upward. 



This may not be a true Stomatopora, but will probably form the 

 type of a new genus, and is only provisionally referred as above. 



Formation and locality. Usually found incrusting the sxirface of 

 Brachiopods ; from the marly beds at Hackberry and Rockford, Iowa. 



Genus — CRANIA Retz. 



Ckania famelica n. sj). 



Plate U, figs. 6, 7. 



Shell small and thin, seldom exceeding one-third of an inch in diam- 

 eter, — the largest seen measuring about four-tenths of an inch ; usually 

 flattened, discoid, tlie apex subcentral and scarcely elevated. Surface 

 marked by distinct lamellose lines of growth, which are often partly 

 obliterated by conforming to the surface of the bodies to which they 

 are attached, as Spikifera and Orthis. 



The only convex example seen, is about half as high as wide, but it 

 is attached to a very convex surface, which must occupy about half the 

 convexity ; usually they are entirely compressed, with the exception of 

 a small area surrounding the apex. 



Formation and locality. In the marly beds at Rockford and Hack- 

 berry, Iowa. 



Genus — STROPHODONTA Hall. 



Strophodonta Canace n. sp. 



Plate 11, flgs. 8-lL 



Shell of medium size, concavo-convex, wider than long, semicircular 

 in outline, or with slightly extended cardinal angles ; cardinal area 

 narrow; area of the ventral valve more than twice as wide as the 

 dorsal, strongly striated vertically, and marked in the center by a narrow 

 lineal callosity. Surface of venti-al valve marked by alternating coarser 

 and finer wrinkled, radiating striie, the stronger ones being most dis- 

 tinct on the most convex part of the valve, where they are sometimes 

 very marked ; from three to five of the finer strire occupy the spaces 

 between the coarser ones. Dorsal valve usually marked with fine, even 

 strise, as fine as those on the interspaces of the ventral valve. 



This species is of the type of S. perjylana, both in the character of 

 stride and the form of muscular impressions of the ventral valve; but 

 the general expression of tlie exterior of the ventral valve strongly 



