Io8 GASTEROPODS. 



broad, shallow umbilicus and regularly rouided whorls. In 

 many examples of this species the volutions are barely in con- 

 tact with one another, and in a few instances the outer whorl, 

 toward the aperture, has actually become separated from the 

 adjoining inner turns. This fact is of special interest as illus- 

 trating the first noticeable departure toward certain evolute 

 Straparolli, which have been referred to Phanerotinus of Sow- 

 erby. 



Straparollus ammon (WHITE & WHITFIELD). 

 Plate 11, fig. 6. 



Euomphalus ammon White & Whitfield, 1862: Proc. Boston Soc. Nat. 



Hist., vol. VII, p. 307. 

 .Straparollus ammon Keyes, 1889: Proc. Acad. Nat. Sci., Phila., p. 295. 



Shell small, with rounded whorls, spiral portions raised 

 but little above the plane of the body volution. Surface 

 smooth, with numerous fine lines of growth. 



Horizon and localities. Lower Carboniferous, Lower Bur- 

 lington limestone: Lousiana (Pike county). 



Straparollus latus ( HALL ). 



Plate li, fig. 9. 

 Euomphalus latus Hall, 1858: Geology Iowa, vol. I, p. 605, pi. xxii, 



figs. 7a-b. 

 Euomphalus boonensis Swallow, 1863 : Trans. St. Louis Acad. Sci., vol. 



II, p. 99. 



Straparollus latus Keyes, 1889 : Proc. Acad. Nat. Sci., Phila., p. 292. 

 Straparollus latus Keyes, 1890: Am. Geologist, vol. V, p. 196, pi. vii, 



figs. la-b. 

 Straparollus blairi Miller, 1891 : Geol. Sur. Indiana, 17th Ann. Rep., Adv. 



sheets, p. 86, pi. xv, fig. 3. 



Shell rather large, discoid, composed of four to five rather 

 rapidly enlarging volutions, plane above; spire nearly on a 

 level with the upper surface of the outer whorl ; suture im- 

 pressed ; deeply and broadly umbilicate; aperture nearly cir- 

 cular, flattened above. The broad flattened area occupying 

 the upper surface of the volutions is bordered on each side by 

 a distinct carina, the inner being near the sutural line. Below 

 the outer ridge are sometimes two scarcely perceptible angu- 

 larities, one around the periphery and the other along the mid- 



