20 TRANSACTIONS OF THE WAGNER FREE 



Family LIMNyEID^. 



Subfamily PLANORBIN^. 



Genus PLANORBIS Guettard. 



Planorbis Conanti n. s. 



Plate 10, figures i, i a. 



Caloosahatchie marl ; not uncommon in the lower beds, more and more 

 abundant toward the top, excessively numerous in the uppermost layer, and 

 forming, with the next species, the most conspicuous fossil in the thin bed of 

 silicified mud which covers the marl-beds near Fort Thompson on the Caloo- 

 sahatchie and extends to Tampa Bay, where it has been dredged up from the 

 ship channel off Ballast Point in large masses. 



Shell large, flattish, sinistral, six-whorled ; sculpture of fine transverse 

 grooving, feebler on the later whorls, especially toward the periphery ; spire 

 with the whorls not carinated, except possibly some of the earlier ones and 

 these but rarely; the upper surface has the angle outside of the suture 

 rounded over with the sutural slope steep, the other nearly horizontal, then 

 rounding downward ; the highest part of the whorl is at this angle ; lower 

 surface of the whorls rather evenly rounded between the sutures and not 

 markedly depressed toward the centre; four or five of the six or seven whorls 

 composing the shell are plainly visible ; the suture deep and prominent on the 

 base ; strongly marked but less deep on the summit of the shell ; aperture 

 very slightly inflated, its base not descending in normal specimens below the 

 plane of the base of the shell, and above hardly rising above the plane of the 

 last whorl ; it is very oblique, sharp-edged, the lower edge preceding, with a 

 thin callus over the body, and no canipanulation. Max. diam. of shell 27.0 ; 

 min. diam. 21.0; alt. lO.O mm. 



This shell is nearest P. Duryi VVetherby, and may be distinguished from it 

 by the following characters : It is larger than P. Djiryi and proportionally 

 flatter ; when P. Duryi is viewed in profile the rounding of the shell from the 

 periphery is notably symmetrical ; in P. Conanti the base is rounded, the upper 

 surface more obliquely flattened and with the highest part nearer the suture 

 and the sutural descent of the whorl more abrupt ; P. Conanti has one more 

 whorl than P. Duryi, and has two more whorls visible on the base, which has 

 not the central funnel-shaped umbilicus of P. Duryi. This last is perhaps the 

 most obvious character on a hasty examination. It will also separate P. Co- 

 nanti instantly from P. lentus and the various forms of trivolvis. 



This species is named, at the request of Mr. Joseph Willcox, in honor of 

 Mr. Sherman Conant, General Manager of the Florida Southern Railway, to 

 whom we are under obligations for courtesies extended which much facilitated 

 the work of exploration. 



This shell is subject to extraordinary deformities, and sometimes, even in 

 rather small specimens, will show seven well-formed normal whorls on the 

 upper surface. 



