592 NORTH AMERICAN INDEX FOSSILS. 



rr. Body whorl inflated, aperture forming more than half 



the length of the shell CC. Cinulia. 



rr. Body whorl not inflated, aperture less than half the 



shell length CCI. Ringicula. 



777. Outer lip neither reflected nor thickened, without col- 

 umellar plications, sometimes with small teeth or tu- 

 bercles in peristome XC. Gibbula. 



II*. Spirals and transverse sculpture equally developed or nearly so... s. 

 s. Inner lip thickened with angular emargination in middle. 



XCV. Neritopsis. 



s. Inner lip not thickened, smooth 888. 



888. Vertical sculpture oblique, rib-like folds. 



CXI I. Vanikoropsis. 

 888. Vertical sculpture interrupted transversely so as to produce 



only rows of tubercles LXIX. Trachydomia. 



II*. Transverse sculpture or ribs alone present; spire low, shell narrow- 

 ing anterior-wards, ribs only near suture. ..CCIX. Rhytophorus. 

 11*. Faint spirals alone present CXX. Campelomu. 



III. Surface with nodes or spines 9» 



9. Shell non-umbilicated 12*. 



12*. Whorls few, rapidly and regularly enlarging, surface nodose. 



LXIX. Trachydomia. 



12*. Whorls few, forming irregular spiral which is sometimes conical, 

 base flat, formed by extended last whorl ; surface irregularly 

 spinose CVIII. Calyptrcea* 



9. Shell umbilicated when not wholly uncoiled 13*. 



13*. Spines irregular, tubular, last whorls mostly uncoiling. 



LXXIV. Platyceras. 



D. Shell in general form like the preceding group, but with the roundness of the 



whorls modified by one or several strong angulations, often flattened ; no 

 marginal notch or slit IV. 



IV. Shell umbilicated 10. 



10. Angulations few (3-5), with all or most of the spaces between them flat- 



tened or concave LXIV. Trochonema. 



10. Angulation only on upper surface or around umbilicus or both 14*. 



14*. Naticoid, high-spired with flattened shoulder and oblique lip. 



LXI. Omphalotrochus. 

 14*. Spire low or flat, the upper carina in center of whorl. 



LVII. Enotnphalus. 

 14*. Spire low, embracing to marginal angulation, last whorl free. 



LVI 1 1 . Calawops* 

 14*. All whorls disconnected, carina on upper surface; well-preserved 



specimens always show apertural notch L1X. Eccyliomphalus. 



14*. Spire flat, coil left-handed (sinistral), angulations on periphery and 



umbilicus LX. Maclurea. 



IV. Non-umbilicated II. 



11. With strong peripheral keel alone modifying the roundness of whorl in 



adult, and with strong oblique folds on upper part of whorl. 



LXX. Turbonopsis. 



E. Shells trochiform, spire more or less continuously conical, basal portion abruptly 



deflected and often flattened. No apertural notch V. 



