97 
EUOMPHALUS * 
Gen. Char. An involute compressed univalve, spire 
depressed on the upper part; beneath concave or 
largely umbilicate. Aperture mostly angular, 
EUOMPHALUS pentangulatus. 
TAB. XLV. — Fig. 1 and 2. 
Spec. Char. A prominent central ridge or rising 
angle on the upper side, the other side obtusely 
angulated. Striae of growth hair-like. Volu- 
tions almost whollyexposed. Aperture obscurely 
pentangular, rounded on the outer side. 
This is apparently a thin shell ; the under and umbilicated 
side is much deeper than the upper, which approaches to 
flat ; there are about six whorls ; the aperture is about one- 
seventh of the diameter of the shell. The striae of growth are 
fine and rising. The greatest diameter is from half an inch 
to two inches. 
From the Black Limestone near Dublin, by favour of 
Mr. T. W. Moore. It is apparently one of the character- 
istic shells of that rock, of which I shall have more to say 
hereafter. The specimen figured is curiously waved with 
a darker and lighter tinted Limestone; it emits a foetid 
odour on being scraped with a knife. The aperture is not 
quite filled up; rhomboidal crystals of nearly transparent 
and whitish Carbonate of Lime form the innermost lining, 
next is the darker Limestone, and then the shell seemingly 
replaced by a mixture of the lighter and darker stone. 
Sometimes the upper side of the shell is very black. I have 
not seen a perfect mouth among a number of specimens, 
although some are otherwise very neatly and finely preserved. 
There may possibly be much larger specimens ; I have some 
very small, about half an inch in diameter. The left hand 
upper figure shows the upper side is flatter than the opposite 
side, which is represented in the right hand figure. Some- 
times the specimens have a more oval form, apparently from 
accident. 
* From eu bene , and o/x^aXog umbilicus. I conceive myself justified in 
giving this Generic appellation, as the shells of which the Genus consists do 
not agree with any Generic character before published. 
