254 THE DEVONIAN OF MISSOURI. 



Order Ctenobranchiata 

 Suborder Platypoda 

 Superfamily Ptenoglossa 



Family Capulidae 



Genus Orthonychia Hall 



Orthonychia belli Clarke 



Plate 67, figure 6 



1908. Platyceras (Orthonychia) belli Clarke, Mem. N. Y. State Mus., vol. 9, pt. 1, p. 

 147, pi. 14, figs. 20, 21. 



Description-— Shell erect, of medium size. The dimensions are: Length about 45 

 mm., width of aperture 30 mm. Outline of shell conical, expanding very gradually but 

 uniformly for about half its length. The expansion becoming more abrupt for the 

 remainder of the distance. Apex missing. Aperture essentially circular, peristome undu- 

 lating. Surface features obscure. 



Remarks — An incomplete specimen only has come under observation. The apex of 

 the shell is lacking, and its character unknown, but the remainder of the specimen 

 seems to conform in all details with the form occurring in the Grand Greve beds at 

 Gaspe. 



Horizon — Upper beds. 



Figured specimen No. 27512, Walker Museum. 



Orthonychia praeconicum sp. nov. 

 Plate 68, figures 1, 2 



Description — Shell of medium size, erect, conical to pyramidal, apex missing; 

 height approximately 35 mm., maximum width of aperture 26 mm. Body volution 

 entirely straight, expanding rapidly and becoming extremely ventricose, marked with 

 four or five well-defined longitudinal ridges and depressions, which become obsolete 

 about one-third of the distance from the apex. The depressions are broad and shallow 

 in the middle of the shell, and become still broader and more conspicuous near the 

 aperture; ridges round. and prominent. Aperture having a sub-triangular outline; 

 peristome apparently deeply sinuous. 



Remarks — This species approaches Platyceras {Orthonychia) conicum Hall, but has 

 a more pronounced pyramidal outline, and the aperture is more distinctly quadrangular. 

 On the small patch of shell which remains attached to the casts, no trace of nodose 

 striae such as characterize the above-mentioned species has been observed. It is of 

 interest to note that the Little Saline specimens show a closer resemblance to the Hamil- 

 ton examples that have been figured than to those from the Onondagan. 



Horizon — Upper beds. 



Holotype No. 27528, Walker Museum. 



Orthonychia tortuosa (Hall) 

 Plate 67, figures 7-10 



1859. Platyceras tortuosum Hall, Nat. Hist. N. Y. Pal., vol. 3, p. 472, pi. 113, figs. 



1-5, 1861. 

 1908. Platyceras tortuosum Clarke, Mem. N. Y. State Mus., vol. 9, pt. 1, p. 146, pi. 



14, figs. 22-25. 





