6 



Indiana University Studies 



posterior end of the shell, just in front of the gaping end. Length of shell 

 75 mm.; height near aperture 27.5 mm.; height at the beaks 30 mm. The 

 length of the hinge is 49 mm. The beak is 24 mm. from the anterior end. 

 Transverse diameter is 24 mm. 



From the top of the Neosho formation ; railroad cut west of Goose Creek, 

 west of Cambridge, Kansas. 



The pallial line seems to be divided for some distance back of the anterior 

 adductor scar. The shell is most like C. leavemvorthana Meek, but it is much 

 more elongate and slender, with ventral and dorsal borders more convex 

 and concave respectively. 



Chaenomya barbouri n.sp. 



The cast is rather large, and is twice as long as the depth at the beak. 

 The beak is convex and appressed, incurved, and located about one-third 

 the way from the anterior to the posterior end of the shell. The cardinal 

 border is deeply concave posterior to the beak, and slopes very gently down- 

 ward in front of it. The ventral border is nearly straight posteriorly, but 

 is convex thruout, and unites with the posterior truncation with a sharp 

 curve. It rounds gradually into the rather broadly rounded anterior margin. 

 The posterior end is very gently convex thruout, otherwise the truncation 

 is nearly vertical, scarcely flaring, and is elliptical in form. The lunule 

 appears to have been rather elongate. The umbonal ridge is subangular 

 at the beaks, but gradually fades towards the lower posterior end. Above 

 this ridge is a somewhat flattened area upon which the large posterior 

 adductor is located. There is a slight flattening of the cast for a short dis- 

 .tance below the beaks, but no distinct concavity. Broad, low undulations 

 are seen over the shell below the beaks and umbonal ridges, otherwise, no 

 surface marks are impressed upon the cast. 



The anterior adductor is located rather high and very near the anterio- 

 border, and the pallial line, faintly erenulated, is double just below it. Thru- 

 out its horizontal length the pallial line is located near the ventral margin 

 of the shell. It is acutely sinuate at its posterior end, above which it is 

 gently convex forward. The posterior adductor is quite large and well 

 impressed, and lies about two- thirds the distance from the beak to the 

 posterior end of the shell. It is roughly quadrangular in form. Length 

 of shell 71.5 mm.; length of hinge 58 to 60 mm.; height at the beak 34 mm.; 

 thickness of valves about 30 mm. 



From the Fort Riley hmestone; Nebraska State line, south of Blue 

 Springs, Nebraska. Professor Wilbur C. Knight, collector. 



Upon cursory examination this species might be mistaken for C. leaven- 

 worthana Meek, which it closely resembles. However, its more curved form, 

 and the more remote location of the beak from the anterior margin, will 

 separate it from that species as well as from C. cooperi (Swallow). Its robust 

 form, the elliptical form of the posterior, as well as its general appearance, 

 separate it at once from C. cylindrica. 



Chaenomya meekana n.sp. 



Shell of moderate size, twice as long as high, beaks remote from the 

 anterior margin. The dorsal margin is very straight for this genus. The an- 

 terior end is rather sharply rounded, while the ventral margin is very slightly 



