55 
Formation and Locality. Three specimens were found in 
the Chazy: Aylmer limestone at MacLaren landing. 
Eotomaria rotunda n. sp. 
Plate IV, figures 5, 6, 7 
Figure 6. Comparison of umbilicus slope and upper surface of 
A. Eotomaria rotunda n. sp. 
B. E. supracingulata. 
C. E. dry ope 
Width 21 mm.; height 14 mm. 
The shell has four whorls', gradually expanding. Aperture 
not well preserved, but a portion broken out of the last whorl 
shows a section very similar to E. supracingulata. The band 
is on the upper side of the whorl, which is concave from the 
band to the suture line. Each whorl rises a little above the 
outer one next it, giving a slightly turreted effect. Umbilicus 
large, being considerably more than one-third the width of the 
shell. Surface markings obliterated, except faint indications on 
one whorl, which as far as they go correspond to the markings 
of E. supracingulata. It differs from E. supracingulata , however, 
in size, in having the upper portion of the whorl concave on 
the whole surface from the band to the suture line, instead of 
being convex on the upper portion of this surface, and in more 
abrupt walls of the umbilicus. The size and upper surface more 
nearly correspond to Eotomaria dryope , though unlike E. rotunda 
Billings, species has narrow but marked convexity of the upper 
surface of the whorl near the suture line. The greatest differ- 
ence, however, is shown on the under side. In the MacLaren 
Landing species the under side of the whorl is more evenly 
rounded and almost flat in the middle, making a rounded drop 
to the umbilicus. The sides of the umbilicus of E. supracingu- 
lata have a more gradual slope and the section of the whorl is 
