GASTEROPODA OF THE LOWER GREEN MARLS. 137 
perforation, representing the comparatively slender solid columella; the 
base of the cast is marked by a rather deep, narrow, spiral groove, about 
one-third to one-fourth of the width of the volution from the umbilical 
cavity, marking the position of an internal spiral ridge at this point on the 
inside of the basal portion of the shell; volutions flattened in the direction 
of the spire, with moderately distinct suture lines separating them in the 
sasts, their surfaces closely and deeply scarred by the attachment of foreign 
substances to the outside of the shell during life. 
This species has generally been considered the same as the Trochus 
leprosus of Morton, Xenophera leprosus of this work, but was described as a 
distinct species, first by Dr. Tuomey, and subsequently made the type of 
the genus Endoptygma by Mr. Gabb. I do not think it is always an easy 
matter to distinguish them, as the groove may not always be present, and 
in other respects there are no constant differences that I can discover. On 
one large cast, which I have referred to Morton’s species, there is an indica- 
tion that the apertural ridge was just appearing, while in the younger 
stages of the shell no evidence of its existence appears. In much younger 
individuals of this form it is strongly marked. It may be that both forms 
should be referred to the same species, in which case the present genus 
would have to be abandoned. 
Formation and locality: In marls of the Lower Beds near Burlington, 
New Jersey. 
SCALARIID 2. 
Genus SCALARIA Lamarck. 
SCALARIA (OPALIA) THOMASI? 
Plate xvin, Fig. 1. 
Seala (Opalia) Thomasi Gabb: Proc. Acad. Nat. Sci., Phila., 1876, p. 296. 
Shell slender, turreted, whorls numerous, closely coiled and very ven- 
tricose, with rather close sutures, numbering seven or more in a specimen 
of less than seven-eighths of an inch in length; apical angle less than 30°, 
probably not more than 25°, the specimen being too imperfect to allow of 
positive measurement; aperture apparently round and the base of the volu- 
