cragin.] DESCRIPTIONS OF SPECIES. 97 
I have not been able to ascertain the maximum height of this shell, 
nor with certainty the number of whorls; but in 1 specimen only 
4 mm. in breadth and about 17 mm. in height there are 15 whorls pre- 
served, while probably 2 or 3 minute ones have been dissolved away 
at the summit. 
The revolving lines of ornamentation on this shell are very delicate 
and commonly are not seen at all on weathered specimens. 
In its internal ridges, as well as in the form of its whorls, the spe- 
cies resembles the Corallian form, N. goodhallii Sowerby." It is 
named for the Messrs R. R. and R. W. Goodell, in recognition of 
their joint exploration of the Malone, an account of which has been 
given elsewhere. 
For comparison with Nerinea goodellii, Doctor Stanton has handed 
the writer some fragments and fragment al prepared sections of a Ne- 
rinea " broken from the hand specimen that bears the larger of the 
.types of Trigonia taffii Cragin." h These resemble A 7 , goodellii super- 
ficially, but appear to lack revolving lines and to present sectional 
idetails which seem to refer them to a different species, although the 
unsatisfactory state of their preservation forbids full assurance that 
their internal characters are all correctly understood. In the Nerinea 
Jfrom Bluff Mesa the fold on the outer wall is relatively thicker and 
[more obtuse and is altogether larger than in N. goodellii, extending a 
(little more than half way across the chamber; the lower columella!* 
if old is also coarser than that of N. goodellii. The upper columella r 
tfold is not very clearly indicated; if present at all it is apparently 
i obsolescent, or at least much smaller than that of TV. goodellii. 
Nerinea circumvoluta sp. n. 
PI. XXI, figs. 4, 5. 
Shell cylindrieal-turriculate; walls thin, with one outer and two 
columella!* folds situated as in the much more common Nerinea 
goodellii, all of the folds delicate, the outer one less so than the other 
wo; columella solid, rather slender; whorls flat or only very slightly 
oncave, one and a fourth times as high as wide, apparently at least 
is numerous as in .V. goodellii, presenting an imbricated appearance 
at the suture, as if the outer wall of each whorl slightly overlapped 
a Described and figured in exterior and in section by James de Carle Sowerby, in Dr. 
William Henry Fitton's " Observations on some of the strata between the Cbalk and the 
Oxford Oolite in the Southeast of England ; " Trans. Geol. Soc. London. 2d ser., vol. 1. 
1836. Sowerby's figures (12 of PI. XXIII, loc. cit.) represent it as several times larger 
than the shell here described as goodellii. The figures 1294 of the fourth edition of 
Dana's Manual are partial and much reduced copies of Sowerby's figures, but, unlike the 
latter, represent the shell as thick-walled. 
J & The large valve from Bluff Mesa, which is the real type of this Trigonia. See remarks 
ion Trigonia taffii on page 10. 
Bull. 266—05 m 7 
