MADE BY DR. A^^TONIO RAIMONDI IN PERU. 211 



pronounced on the upper surfaces, near and adjoining the suture. Towards the 

 base there are a few very faint rudiments of revolving lines. 



Figure. Somewhat enlarged. 



Locality. Liassic coal mine of Pariatambo ; and from the elevated table-land 

 two leagues from Cajaraarca, 



Remarks. This shell possesses remarkable interest from its being the first spe- 

 cies of its group of Naticas, found outside of the Upper Cretaceous. Its evidence, 

 however, of a Cretaceous age of the deposit is counterbalanced by the presence of 

 Mi/ophoria and by the close relationship of the associated Ammonites to Liassic 

 types. While possessing every character essential to the genus, of which I am 

 acquainted with almost every described species, it differs from its congeners in 

 having the characteristic umbilicus, but unusually narrow; an amount of difference 

 that is not surprising when we consider the difference in geological age. 



G. LiRATA, n. s., PI. 39, flg. 6, 6a. 



Shell subglobose, large; spire elevated; whorls broadly convex, but very slightly 

 oblique, somewhat flattened on the top and regularly rounded on the sides; umbil- 

 icus patulous ; aperture not very oblique. Surface marked by about five slightly 

 raised revolving ridges crossed by well-marked lines of growth. 



Figures. Natural size. 



Locality. " Near Ollon, Prov. of Cajatamba. Height more than 3000 metres." 

 Cretaceous. 



Remarks. One of the largest species of- the genus yet discovered. It is at once 

 distinguished by a character, rare in the family — surface sculpture. One or two 

 species of Gyrodes are crenate on the upper or lower margin of the whorls, but 

 this has distinct revolving ridges placed at about equal distances over the whole 

 surface. The only specimen is a cast retaining enough of the shell to show all of 

 the specific characters except the details of surface adjoining the suture. The 

 cast shows that the upper part of the whorl was more or less flattened, but does 

 not show if the margin of the flattened space was acute, rounded, or crenate. 

 The internal mould shows no trace of the surface ridges. 



PRISCONATICA. N. Gen. 



Among the earlier forms of Naticas (those of the Secondary rocks) is a large 

 group that has been described, almost without exception, under the vague generic 

 title of Natica. They are characterized by being almost always of large size, 

 including several of the largest known species of the family; by their thin shells, 

 generally elevated spire, increasing rapidly in their axial length, rather than 



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