Weller — Kinderhook Faunal Studies. 167 



the ridges, as if for the attachment of setae. No appearance 

 of plications has been observed on any of several specimens 

 examined." 



Length of an average specimen 15 mm., breadth 19 mm., 

 convexity of pedicle valve 5 mm. 



Remarks. Spirifer Jtirtus W. & W., described from bed 

 No. 5 at Burlington, is a synonym of the species described 

 from the Chouteau limestone of Cooper County, Missouri, as 

 S . cooperensis Swall. The species is a common one in the 

 fauna under consideration and is scarcely more than a diminu- 

 tive form of R . pseudolineata (Hall) from the Osage faunas. 

 The median septum and dental plates of the pedicle valve, 

 represented by narrow slits in the specimens, are conspicuous 

 features of the species as it occurs in the yellow sandstone in 

 the form of internal casts. The brachial valve is marked 

 only by a somewhat faint median septum. 



Cyrtina acutirostris (Shum.)? 



Pi. XIV. f. 5. 



This species is represented by a single specimen of a 

 brachial valve. It agrees in all respects, except such as may 

 be due to differences of preservation, with specimens from 

 the Louisiana limestone. Additional specimens, however, 

 showing the opposite valve, will be necessary for study before 

 this identification can be made with certainty. 



MOLLUSCA. 



PELECYPODA. 

 Pterinopecten nodocostatus (W. & W. ). 



PI. XV. f. 7. 



Aviculopecten nodocostatus, Bull. U. S. G. S. 153: 113. . 



Original description. '« Shell of medium size, semi-circu- 

 lar in outline, valves depressed convex. Hinge line straight, 

 equalling the greatest width of the shell. Anterior extension 

 separated from the body of the shell by a deep marginal 

 sinus, and by a broad flattened depression on the surface, 

 extending from the beak to the extremity of the auricle ; pos- 



