262 
excessive tliinness of its shell, and by the almost complete ahsenee of the lines 
of growth on its surface. It differs also by the fibrous structure of the shell, 
a structure not possessed by the species to which I have compared it. 
Horizon and Localities. — It is rather abundant in a greenish, 
arenaceous limestone at Harper’s Hill, where it is associated with a great 
number of Murcliisonia trifilata, Dana. One specimen was found in a 
yellowish sandstone at Branxton. 
Euompiialus minimus, F. 3IcCoy. 
PI. XXIII, Pig. 17. 
Enomphalus minimus, P. McCoy, 1817, Ann. Mag. Nat. Hist-., XX, p. 305, pi. 17, fig. 4. 
Tiiis is an extremely small, rounded shell, composed of three or four 
eonvex spiral whorls, with a grooved suture, and a depressed spire. The 
last whorl is relatively well develojied and convex at the base. The umbilicus 
is small; the aperture transversely oval; and the surface smooth. 
Dimensions. — The diameter of the largest specimen I have seen does 
not exceed two millimetres ; its length is nearly half that. 
Relations and Differences. — As this is rather abundant in certain 
Carboniferous rocks in N.S. Wales, wdiich contain no Enomphalus of a larger 
size at all like it, this probably really constitutes a distinct sj)ecies, and is not 
a young individual of a larger one, as might be thought. I know of no other 
Carhoniferons Enomphalus to which it could he compared, or with ■which it 
could be confounded. 
Horizon and Localities. — According to McCoy this species is common 
in the shales of Hnnvegan. Mr. Clarke found several specimens in the 
argillacoiis limestone at Burragood. 
