370 TRANSACTIONS OF THE WAGNER FREE 



and, therefore, that Gray's name, being later, must be given up. But Guild- 

 ing's type forms a Hnk between Polynices proper and MainiJiilla,i\\e. umbih'cus 

 being usually open and the shell moderately thin ; but occasionally the former 

 is solidly filled with callus and the shell is thick, so that it cannot be distin- 

 guished from a typical Polynices. Therefore, we are not obliged to reject 

 Gray's name, which has become so familiar for the type to which it was applied. 



The fossil species which appear to be referable to Lunatia are often puz- 

 zling from their relations to the other subgenera, especially in the Eocene, 

 so that it cannot be positively asserted that in all cases our conclusion is final. 

 But, under the circumstances, it seems best to refer to Lunatia all those fossil 

 species having the general form of the recent species of Lunatia, and of which 

 the opercula are unknown. The number in our Tertiary is quite considera- 

 ble, and several of them show traces of affinity with typical Naticas, which 

 among the recent species have vanished. The groups which are sharply 

 limited in the recent fauna blend into one another as we trace their ancestry— 

 as has already been noted by Zittel and others ; a result at which no evolu- 

 tionist will feel surprise. 



Omitting the Pacific Coast species, the Eocene forms of our Tertiary may 

 be briefly summarized as follows ; 



L. iiavtonensis Meyer and Aldrich (1886) is known by its small, depressed 

 spire, appressed suture, flattened and shouldered last whorl, solid shell and 

 small umbilicus ; it is known from Prairie Creek and Lisbon, Ala., Newton, 

 Meridian, Enterprise, and the Wahtubbee Hills, Miss. It has been figured 

 by De Gregorio under the name of semihinata Lea, which latter species he has 

 not recognized. 



L. minima Lea is a thinner shell than the preceding and more elevated ; 

 its prominent characters are its rounded whorls, deep suture, its excavated 

 and often spirally striated umbilicus, with the pillar thickened only near the 

 body, and very little reflected there. It reaches an altitude of 19 and a breadth 

 of 20 mm., and is known from Claiborne, Wahtubbee Hills, Wood's Bluff, 

 etc., and is especially abundant in the Jackson horizon. A species named L. 

 Tuomeyi by Prof Whitfield, from the Old Miocene marl of Jericho, N. J., 

 does not seem to differ from L. minima, except, perhaps, in not reaching so 

 large a size as the majority of Eocene specimens. Lea's type is a very young 

 shell, but recognizable. De Gregorio figures an extremely minute young 

 shell under the varietal name of pnsillinscii/a, but I cannot see why it should 

 have been named. 



L. pcrspccta Whitfield (1865) is of about the same size as L. minima, 

 from which it differs by its somewhat .smaller umbilicus, more polished sur- 

 face, and by having a spire like that of Neverita ihiplicata in miniature. The 

 suture is usually minutely channelled. We have it from the Prairie Creek 

 beds, Matthews' Landing, and Claiborne, Ala. 



L. vicksbnrgensis Conrad (1848) is a shell of the shape of the recent L. 



