10 BULLETIN NO. 2. 



ridge extending diagonally from the beak to the posterior extrem- 

 ity of the ventral margin. Dorsal margin straight from the beaks 

 to the obHquely truncated posterior margin. 



Beaks long, strongly recurved, and projecting about f of an 

 inch beyond the dorsal margin. 



Length 3j\ inches; height 2t'v inches; convexity of the valve 

 about ^ inch. 



This is the largest species of Schizodus hitherto found in this 

 State, and is from one of the upper divisions of the Chester lime- 

 stone, about two miles below the mouth of Marys river, Kandolph 

 county. 111. 



No. 24'c8 of the Ilhnois State collection. 



Collector, A. H. Worthen. 



SCHIZODUS VAKSOVIENSIS. (sp. UOV.) 



Shell of medium size, transversely ovate, moderately convex in 

 the anterior and umbonal regions, cuneate posteriorly ; anterior 

 side very short and regularly rounded; basal margin forming a 

 very gentle curve that is most prominent near the anterior mar- 

 gin ; posterior extremity contracted and narrowly rounded ; dorsal 

 margin nearly straight, beaks depressed, incurved and located 

 about one-third the length of the shell from the anterior margin. 

 Surface markings unknown. 



Length of an internal cast in Hmestone 1| inches; height of 

 same |- inch, convexity about f inch. 



This species may be readily distinguished from *S'. Chester ensis, 

 which it approaches in size and form, by its relative proportions 

 and more depressed beaks. 



Position and locality : The upper part of the Keokuk limestone, 

 Warsaw 111. 



No. 250J of the Illinois State collection. 



Collector, A. H. Worthen. 



SCHIZODUS NAUVCOENSIS. (sp. nOV.) 



This shell is only known from a cast of a single valve in lime- 

 stone, but it differs so decidedly from all others of this genus, 

 that it may be readily characterized as follows: 



Shell above the medium size, obliquely sub-ovate, rather strongly 

 convex from the beak obliquely downward for about half the length 

 of the valve, and thence gradually depressed to the ventral mar- 

 gin; anterior extremity regularly rounded from the dorsal to the 

 ventral margin, posterior side oblique, the marginal line curving 

 in below the beak; ventral margin not entire, beak pointed, ele- 

 vated and incurved, and situated near tbe anterior margin, sur- 

 face markings unknown. A well-defined ovate muscular scar is 

 conspicuous just below thu Leak, and near the anterior border of 

 the shell. 



