188 PAL.EONTOL'JGY. 



face-marking can be seen. This is continuous over the sutiu'e, and covers 

 all the volutions of the spire. At first, I was inclined to think that it might 

 have been secreted by the mantle of the animal enveloping the whole shell; 

 hut further examinations have led to the conclusion that it is more probably 

 merely an inorganic incrustation precipitated over the surface after the death 

 of the animal, as some of the other types from the same beds are similarly 

 covered. 



This shell approaches the aspect of the typical form of the genus 

 Carinifex, but still wants the characteristic carina of that type. 



Locality and jyosition. — Same as last. 



Carinifex (Vorticifex) Tryoni, Me(^k. 



Plate 17, fiK-*. 10, 10 a, 10 6, 10 c. 

 Carinifex [Vorlicifex) Tryoni, Meek (Ap., 1S70), Proceed. Acail. Nat. Sci. Pbilad., 59. 

 Carinifex ( Vorticifex) Tryoni var. concava, Meek, ib. 



Shell depressed-subglobose, approaching subdiscoidal, the spire being 

 much depressed. Volutions four and a half to five, increasing rather rap- 

 idly in size; those of the spire slightly convex ; last one sometimes becoming 

 a little concave on the upper slope near the aperture, and more or less ven- 

 tricose below, the most prominent part being near the rather small, deep • 

 umbilicus, into which its inner side rounds abruptly; all thte whorls rounded 

 on the outer side, and without any traces of carinse or revolving markings; 

 suture well defined; aperture rather large, subcircular, its height being to its 

 breadth .about as 29 to 34; lip sharp, oblique, and produced forward above, 

 faintly sinuous at the middle of the outer side, as well as at the inner side 

 of the base, where it is a little thicker. Surface ornamented with small, 

 distinct, regular ridges, and much finer lines of growth, running parallel 

 to the very oblique outline of the lip. 



Height, 0.35 inch; breadth, 0.64 inch; height of aperture, 0.29 inch; 

 breadth of aperture, 0.34 inch. 



This shell difi"ers from the foregoing species in its smaller size, more 

 rounded, less rapidly enlarging whorls,more prominent spire, and less exca- 

 vated -umbilical region. It evidently varies considerably in form and sur- 

 face-markings, some of the specimens being proportionally more ventricose, 

 or, in other words, have the body-volution, and consequently the aperture. 



