430 Systematic Paleontology 



smooth body-whorl in the adult, all covered with a most elegant and 

 polished glaze ; also by its habit of depositing a band of callus above the 

 suture on the periphery of the preceding whorl. The pillar is stout and 

 slightly curved, and the plaits are three or more, weak and rather variable, 

 somewhat as in Vohitolithes. The sinus at the suture is notable but not 

 very wide. The plaits are preceded on the pillar by a thin mass of glaze 

 which extends over the well-marked siphonal fasciole, somewhat as in some 

 Olivce, but with less defined boundaries. The plaits are not well visible at 

 the aperture and are situated on the thickest part of this callus. These 

 are very beautiful fossils, though poorly preserved in most cases, and the 

 genus seems to me valid."- — Dall, 1890. 1 



The genus is restricted in its known distribution to the Cretaceous. 



A. Callus deposited in an obtuse ridge behind the suture. 



Liopeplum leiodermum 



B. Callus not deposited in an obtuse ridge behind the suture. 



1. Shell compressed dorso-ventrally, the whorls of the spire cyndri- 



cal in outline Liopeplum cretaceum 



2. Shell not compressed dorso-ventrally, the whorls of the spire 



trapesoidal in outline Liopeplum monmouthense 



Liopeplum leiodermum (Conrad) Dall 



Volutilithes (Athleta) leioderma Conrad, 1860, Jour. Acad. Nat. Sci., 2 ser., 



vol. iv, p. 292, pi. xlvi, fig. 32. 

 Lioderma lioderma Conrad, 1865, Proc. Acad. Nat. Sci., Phila., p. 184. 

 Liopeplum lioderma Dall, 1890, Trans. Wagner Free Inst. Sci., Phila., vol. 



iii, pt. i, p. 73. 

 Liopeplum leioderma Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 25. 



Description. — " Subfusiform, smooth, and polished ; spire scalariform, 

 angle callous ; shoulder over the aperture with a projecting callus ; aperture 

 long, effuse ; labrum slightly notched or sinuous at the superior extremity ; 

 columella four-plaited ; plaits very oblique ; superior one obsolete." — 

 Conrad, 1860. 



Type Locality. — Tippah County, Mississippi. 



A slender, much battered individual was collected in the Maryland 

 Cretaceous which suggests L. leiodermum in the development of an obtuse 

 rib of callus directly behind the suture. It is smaller than the type of 



1 Dall, 1890, Trans. Wagner Free Inst. Sci., Phila., vol. iii, pt. i, p. 73. 



