INVERTEBRATES. 141 



Position and locality: Lower division of the Chester lime- 

 stone, Chester, 111. 

 Collector. Mrs. J. C. Salter. 

 No. 2514 of the Illinois State Museum. 



GENUS MURCHISOXIA, D'Arch. and Vern. 



MURCHISOMA KEOKUK. (sp. nOV.) 

 PL XXTTT. Fies. 2-2a. 



Several casts of a long spiral shell have been found in the 

 Keokuk limestone, which seem to belong to the genus Murcbi- 

 sonia, but none of them retain any portion of the test, and 

 consequently nothing is known of their external characters. 



These casts all have an elongated form that tapers very grad- 

 ually to the apex. Volutions about six, the upper ones rather 

 more regularly rounded than the last: suture wide and deep. 

 Aperture apparently ovate. 



Length of a cast with five volutions, nearly 4 inches; great- 

 est breadth of the last volution 1% inches: transverse diameter 

 of the same % inch. 



Position and locality: Keokuk limestone. Keokuk. Iowa. 



The specimens figured were kindly loaned by Mr. L. A. Cox, 

 of Keokuk. 



MURCHISOMA LASALLEXSIS. (sp. nov.) 



PL XXV, Figs. 7-7a. 



Shell turriculate, slender, spire pointed at the summit, com- 

 posed of eleven or more volutions, which are elevated in the 

 middle into a prominent carina, and separated by a profound 

 suture. 



On the last volution there is a flattened band below the ca- 

 rina. which is bounded below by a slight elevation. Neither the 

 flattened band nor the elevation below extend to the other vo- 

 lutions. 



Length of the shell * 4 inch: breadth of the last volution '' 16 

 inch; spiral angle about 22. 



This little shell is closely related to M. sub-angulata, of Ver- 

 neuil and Keyserling*, but differs in the greater number of its 



* Geology of Russia and the Ural Mountains, VoL II, page S40, PL XXII, Fig. 6. 



