704 



NORTH AMERICAN INDEX FOSSILS. 



XCII. Margarita Leach. 

 Trochoid umbilicated shells, with rounded whorls and impressed 

 suture. Cretacic-Recent 



327. M. ornatissima (Gabb). (Fig. 1012.) 



Cretacic. 

 Of naticoid form, umbilicus moderate, apical 

 angle less than in M. abyssina, suture moderately 

 impressed, surface finely spiralled. 

 Fig. 1012. Mar- Nanaimo group of Vancouver ; Chico of Cali- 



garita ornatissima, fomia, etc. 



Gab^f' 328. M. abyssina (Gabb). (Fig. 1013.) 



Cretacic. 

 Four or more volutions ; apical angle 70 or 75°; umbilicus 



* 



Fig. 1013. Margarita abyssina. (After Whitfield. ) 



broad and open ; shell thin, with very fine spirals, and apparently 

 a stronger peripheral one. 

 Ripleyan of New Jersey. 



Family Adeorbiim: Fischer. 



XCIII. Teinostomata Adams. 



Low-spired or discoidal shells, with the broad umbilicus covered 



by callus in the adult ; whorls flattened vertically ; surface smooth. 



Miocenic-Recent. 



329. T. nanum (Lea). (Fig. 10 14.) Miocenic. 



b a c 



Fig. 1014. Teinostomata nanum, much enlarged. (Md. Survey.) 



Shell smooth and highly polished, umbilicus covered by thick 

 callus, bounded by faint impressed line ; spire very low. 

 Chesapeakean of Atlantic coast. 



