50 Bulletin i (50) 



from its acute outer lip. Its Naticoid affinities are beyond ques- 

 tion. 



Type. — Phila. Ac. Fig'd specimen, Harris's collection. 

 MESALIA 



Mesalia vetusta Con. pi. i, fig. 6. 



(See p. 48 of this Bulletin) . 



Conrad has well remarked of this species that it is very abund- 

 ant though rarely perfect. The figure he gives in his Foss. Sh. 

 Tert. Form., 1835 is very misleading ; Lea's is better. This 

 specimen when figured was perhaps as perfect as when first depos- 

 ited. Its apex is slightly eroded. Its aperture, at least when 

 figured, was perfect. 



The direct ancestor of this species is clearly M. daibornensis of 

 the lyOwer Claiborne horizon. This in turn seems to have come 

 from ^'Potamides" alabamiensis Whitf. , of the Lignitic. The 

 Midway contains a large number of varietal forms of P. alabami- 

 ensis. 



Type of the species. — Phila. Ac. Coll. 



Figured specimen. — Texas State Museum. 



ERRATA 



Page 6, line 3; for 44, read 31. 

 Page 6, line 6; for 31, read 44. 

 Page 27, line 25; *for jilnmentosa read Jilamentosa. 

 Page 27, line 31; for m-argarstacea read m.argarita- 

 ceum. 



