3(5 



Found by S. A. Miller, in the Chouteau limestone, six miles 

 from Sedalia, Missouri, and now in his collection. The specific 

 name is in honor of R. A. Blair. 



OONIATITES PARRI8HI, n. Sp. 



Plate IV, Fig. 6, surface Jorm of a sephim; Fig. 7, lateral view; 



Fig. 8, ventral view. 



Shell below medium size, discoid, sublenticular, volutions very 

 rapidly expand. Transverse section of a volution semielleptical. 

 The sides of the volutions are somewhat flattened and inclined to- 

 ward the ventral margin, which is narrowly rounded. The outer 

 volution embraces the inner ones. The umbilicus is small and 

 discloses no part of the inner volutions. The sides of the umbili- 

 cus are abrupt and the greatest transverse diameter of a volution 

 is near the abrupt descent to the umbilical cavity. The dorso- 

 ventral diameter of a volution, in the early growth of the shell, 

 does not exceed the transverse, but the dorso-ventral diameter in- 

 creases more rapidly than the transverse, with the growth of the 

 shell, and soon becomes one-fourth greater, and, probably in older 

 shells than ours, it may become one-half greater. The external 

 shell is unknown. The air chambers are very short and do not 

 increase, in length, in proportion to the increasing size of the 

 volutions. The septa are closely arranged. 



Each septum curves gently from the umbilicus forward aud 

 back to near the middle of each lateral side, where it forms an 

 obtuse retral angle and is directed nearly straight forward to the 

 ventio lateral margin, where it makes an abrupt retral bend and 

 iri directed backward nearly to a line with the first formed angle, 

 aud then again bends forward and makes a forward semicircular 

 curve across the median line of the ventral margin. There are, 

 therefore, five saddles and five lobes, which will be best under- 

 stood by looking at the illustration. The middle saddle curves 

 forward slightly more than the lateral saddles, but the ventro- 

 litteral saddles extend more than twice as far forward and are ob- 

 tusely roumlod at the anterior ends. 



This species is distinguished by the general form of the shell 

 and by the surface form of the septa. 



Found by W. J. Parrish, in whose honor the specific name is 

 given, in the Upper Coal Measures, at Kansas City, Missouri, aud 

 now in the collection of \Vm. F. E. Gurley. 



