Correspondence. 87 
agreements and differences among these shells in their several stages 
of growth were given in this paper, prefaced with some remarks on 
morphological science as illustrated by the Meduse, the Echinoder- 
mata, and Crustacea. ‘The following are Dr, Wright’s conclusions :— 
Ammonites planicostatus, Sow., is the young of Am. Dudressieri, 
D’Orb. It has at first smooth ribs, flattened on the back ; each rib 
then developes a spine near the back, which has become broad and flat ; 
the spines afterwards diminish in size, becoming blunt tubercles, 
and even disappearing altogether in old shells. Am. semicostatus, 
Y. & B., is nearly smooth when young, without the keel or ribs, 
which are prominent in middle-aged shells. Am. bifer, Quenstedt, 
is smooth when young, acquires ribs when older ; and differs con- 
siderably when aged, the ribs becoming recurved processes. Am. 
Jamesoni, Sow., is an adult form, with ribs undulating over the back; 
Am. Reynardi, D’Orb., represents the middle age of the same species, 
with dorsal tubercles on the ribs and no keel; and Am. Bronnii, 
Roemer, is the young form, with ribs, tubercles, and dorsal keel. 
Lastly, Am. capricornus, Schlot., is very difficult to identify in its 
many forms; indeed, no less than six so-called species have been 
described out of the various phases of its growth: in early age it is 
Am. maculatus. Y. & B., and Am. planicosta, VOrb.; a little older 
it is Am. laticostatus, Sow. ; still older, and when the last whorl has 
become suddenly enlarged with two lateral rows of small tubercles, 
it is Am. heterogenus, Y. & B., and Am. Henleyi, Sow. By a careful 
study of the morphological characters which Ammonites exhibit, the 
number of the so-called species will be greatly reduced, and their 
diagnosis simplified. This will be a boon to the paleontologist, now 
that the value of Ammonites is more generally recognized; for 
among all the Invertebrata, they are the surest indicators of the 
stratigraphical position of the different zones of life in the Secondary 
rocks. 
CORRESPONDENCE. 
ee 
EOZOON CANADENSE IN CONNEMARA MARBLE FROM THE 
BINABOLA MOUNTAINS. 
To the Editor of the GroLocicaL MaGazine. 
My pEAaR Sir,—I send you two or three slides with films 
(mounted and ground slices) of the Irish green marble containing 
the fossil which I suppose to be the same as Hozodn Canadense ; in 
fact, I can see no difference whatever. In the hand-specimen, however, 
the Irish differs much from the Canadian, as the best films are got, 
not from the banded dark-green, or from that with blue patches, but 
from the pale-green, translucent, apparently homogeneous portions ; 
that with blue patches showing but little trace of the Foraminiferal 
structure. The quarry producing the best specimens is that on the 
north-west flank of the most south-westerly of the Binabola Moun- 
