498 THE MEDALS OF CREATION. Cuap. XI. 
back of the whorl in Lign. 136; several species occur in 
the Mountain Limestone; the markings of the original 
shell are sometimes preserved, as in the example delineated. 
This genus is common in the Oolite; a splendid species, 
with the shell entire, is found in the Kimmeridge Clay, at 
Hartwell; limestone casts of the same species are abundant 
in the Portland stone at Swindon, in Wiltshire. 
Lien. 136. UNIVALVES FROM THE MounTatIn LIMESTONE. 
Fig. 1.—EvOMPHALUs PENTANGULATUS; upper surface. 
2.—Polished section of the same species. 
3.—NATICA PLICISTRIA. Yorkshire. Mt. L. 
4.—PLEUROTOMARIA FLAMMIGERA. (Phil. York.) Mt. L. 
There are two species of this genus (formerly named 
Cirrus by Mr. Sowerby) which are of frequent occurrence 
in the White Chalk of England, in the state of casts, and 
are figured in my oss. South D. tab. xviii., under the 
names of Cirrus perspectivus, and Trochus linearis. The 
Chalk Marl of Sussex yields in some localities (Hamsey, 
