160 GENESIS OF THE ARIETIDA. 
the original at the Ecole des Mines showed the young of the true Bonnardi to be 
tuberculated, which is not the case with the young of planaries. This fact was 
apparently not observed by Oppel, who considered planaries to be identical with 
the typical Bonnard. It is possible that Conybeart, as figured by Hauer, may 
belong to this variety. 
Vermiceras ophioides, Hyarr. 
Plate I. Fig. 21-23. Summ. Pl. XI. Fig. 25. 
Discoceras ophioides, Hyatt, Bull. Mus. Comp. Zool., I., No. 5, p. 76. 
Amm. ophioides, D’OrB., Terr. Jurassique, p. 241, pl. lxiv. 
Locality. —Semur. 
The young is smooth for one volution and a half. On the third quarter of 
the second, scattered folds begin, developing into true pile on the first quarter 
of the third whorl. During the first half of this whorl, after the keel is devel- 
oped, the rounded sides of the shell show that the form of the whorl, as well 
as the immature pile, resemble Cal. laqueum. 
The abdominal sulcations are well defined on the last quarter of the third 
whorl, and from their well marked character on the early part of this quarter it 
may be inferred that they begin on the third quarter, where, however, they were 
not directly observed. For the same reasons, also, I should infer that there are 
well defined lateral ridges to the sulcations almost immediately after their first 
appearance on this same third quarter. The very rapid appearance of these 
’ characteristics probably prevents a repetition, or only permits a very partial 
one, of the adult characteristics of any of the species intermediate between Calo- 
ceras Johnstoni and Ver. Conybeart. In the course of the growth through the second 
quarter, the sides of the whorls remain rounded and the pile more or less imma- 
ture, as in the adults of /agueum and Johnstom. On the third quarter of this whorl, 
and simultaneously with the channels, the peculiar genicule and squared or 
quadragonal whorl appear, and we find also distinct lateral ridges to the channels, 
a well defined keel, and what seem to be minute tubercles, but are really only 
very angular genicule. 
From this period these characteristics, which render a fragment of the adult 
whorl identical in its aspect with the adult of Conybeari, are increased and 
strengthened, but not otherwise changed by growth. 
The sutures, however, though observed in only one specimen, differ somewhat. 
The lobes and saddles are more pointed and have smoother outlines than in Ver. 
Conybeari. It is a species which illustrates admirably the law of acceleration in 
heredity. 
Canavari,in his work on the Lias of Spezia, figures under the name of Ver. 
(Ariet.) spiratissimum, Plate XX. Fig. 2, a very interesting dwarf, with exceedingly 
narrow channels and linear sunken keel. This is probably distinct, and the name 
supraspiratas subsequently given by this author, in his republication of this paper 
in the third volume of the “ Memorie della Carta Geologica d’ Italia,” to the same 
