102 



NORTH AMERICAN INDEX FOSSILS. 



126. D.lasallense (Meek and Worthen). (Fig. 1326.) Carbonic. 

 Whorls subquadrangular with rounded angles and ventral flat- 

 tening. Enlargement very gradual. Surface smooth. 



Coal Measures of Illinois, Iowa, etc. 



XLV. AsYMPTOCERAS Ryckholt. 

 Nautilicones with broad dorsum and lateral expansions towards 

 the aperture; section of whorls depressed elliptical to hemispheric; 

 surface smooth; siphuncle subventran. Carbonic. 



127. A. newloni Hyatt. (Fig. 1327.) Carbonic. 



I 

 I 



Asympioceras newloni, X Vi- (After Hyatt, Texas Survey, II. 



Venter broad, marked by two faint flattenings or concavities, 

 separated by faint median ridge. 

 Coal Measures of Kansas. 



XLVI. SoLENOCHEiLUS Mcck and Worthen. 

 Similar' to preceding but whorls less rapidly enlarging; siphuncle 

 small, in contact or nearly so, with venter; lip auriculate near 

 dorsal angles. Mississippic-Carbonic. 



128. S. collectus Aleek and Worthen. (Fig. 1328.) 



Mississippic-Carbonic. 



Subquadrangular; venter gently rounded; sides flat; involution 

 moderate, umbilicus small but profound. 



St. Louis of Indiana, Illinois, etc. ; Carbonic of Texas. 



