DUBLIN NATURAL HISTORY SOCIETY. 
33 
the umbilical margin as fully developed as any fossil or recent So¬ 
larium. 
Mr. Phillips founds the genus Euomphalus on the character that in the 
old shells the upper portion of the* shell is partitioned off by the animal, 
which was provided with the means of depositing a septum of shell oc¬ 
casionally, after the manner of the chambered Cephalopoda. There 
was no communication, however, kept up between the chambers and the 
body of the animal, as in the Cephalopoda. This character, however, is 
far from being well established as a general characteristic of the Euom¬ 
phalus, having been only established in some of the species, as JE. 
pentangulatus, JE. acutus, and E.pugilis. M. de Koninck maintains that 
all the species of Euomphalus have the external lip slit, like Pleuroto- 
maria,—a circumstance which, if true, would undoubtedly require us to 
remove them from the family of the Trochidae into that of the Halio- 
tidee. The character noticed by M. De Koninck is found in some of our 
Irish Carboniferous species, and is beautifully exhibited in a specimen, 
JE. regince (Haughton) found by me at Sheffield, Queen’s County. This 
specimen would be referred at once to E. acutus, were it not for the 
accidental preservation of a portion of the shell and of its original co¬ 
louring and markings, which show that it had a deep slit in the exterior 
lip, and a sinus band, not distinguishable from that of many species of 
Pleurotomaria. 
While the Euomphalus thus approaches Pleurotomaria in some of 
its forms, it connects itself with Haliotis in the remarkable species ge¬ 
nerally assigned at present to Cirrus (not Sowerby). There are three 
species of this kind known in the Palaeozoic period:— C. cristatus of Ire¬ 
land, C. Goldfussi of the Eifel, and C. armatus of Belgium. These fossils 
have the form of Euomphalus, and are provided with a series of aper¬ 
tures on the upper surface of the spines, prolonged into tubes, similar in 
some instances to those of the Haliotidae, and of these tubes the anterior 
remain open, while the posterior tubes are gradually closed up. We 
thus see that while Euomphalus, in its ordinary forms, belongs to the 
group of low-spined Trochidae, yet that it keeps up the most intimate 
relations with Pleurotomaria and Haliotis; so far as mere form is con¬ 
cerned, Euomphalus cannot be separated from Cirrus; and yet the 
structure and habits of the animals inhabiting the two kinds of shells 
must have been very different, as the breathing apparatus indicated by 
the short tubes of Cirrus was of a totally different character, from that 
of Euomphalus. 
If we were to judge by mere form, there would be the greatest dif¬ 
ficulty in separating Cyprina from Yenus; and yet even a palaeontolo¬ 
gist could tell that they differed, by the impression of the mantle on the 
shell. 
But, although I admit that slight differences, where they indicate 
physiological structure, are and ought to be of importance, I may be 
allowed to doubt if they are as important to the geologist as to the zoo¬ 
logist. It must not be forgotten that, although Geology throws much 
light on some branches of Natural History, in filling up lacunae in our 
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