THIRD, OR VERMICERAN BRANCH. 141 
Caloceras laqueum, Hyarr. 
Summ. Pl. XI. Fig. 22. 
Amm. laqueus, Qurnst., Amm. Schwab. Jura, pl. xviii. fig. 4; pl. i. fig. 14 (not fig. 15, 16). 
Amm. intermedium, Porti., Geol. Londonderry, p. 186, fig. 17. 
4igoceras intermedium, Wriaut, Lias Amm., p. 314, pl. xv. fig. 3, 4 (not fig. 5, 6) 
igoceras Belcheri, Wriaut, Ibid., p. 313, pl. xv. fig. 7-9 (not plo eke NO do), 
Ariet. Scylla, Win., Unt. Lias, Mojsis. et Neum., Beitr., VI. 1887, plexes lio: 758; 
Amm. Scylla (pars), Reyné&s, plates. 
The youngest specimen I have yet seen of this species was 26 mm. in 
diameter. The abdomen, however, was smooth, with no indications of the 
immature keel of the adult, the sides exceedingly gibbous. The pile evidently 
began early, and were closely crowded and slightly curved forwards. 
In one specimen the pile were very slightly developed in the adult; in 
another, at a corresponding size, they were already disappearing, and upon the 
next or senile whorl they were almost obsolete. The keel probably becomes 
very slight at this time, and the likeness to its own young must then have 
been remarkably close.’ This specimen was 53 mm. in diameter. 
The similarity of the adult of this species to the young of Ver. spiratissimum 
is unmistakable. A specimen from Bebenhausen, in Quenstedt’s collection, shows 
that the sutures are intermediate between those of Cal. Johnston’ and those-ot 
Ver. spiratissimum. The young of a specimen from Oestringen in Fraas’s collec- 
tion, Stuttgardt Museum, when about 26 mm. in diameter, has the exact form 
and characters of Quenstedt’s figure, but no signs of a keel, though this appears 
soon afterwards. A fine series in the Semur Museum shows that the keel may 
not yet have arisen in a specimen at the diameter of 45mm. The whorl also 
at the time of the appearance of the keel may have either a broad, depressed 
abdomen, as in the varieties which approximate to the young of Ver. spiratissi- 
mum and carusense, or this part may be elevated, as in Cal. tortile. 
The young, however, are like the young of Cul. Johnston’. The sutures also 
vary in the same way, some specimens having sutures like those of Johnston, and 
others approximate to those of carusense and spiratissinum. Old age in all these 
was marked by narrowing of the abdomen, loss of the keel, etc., which probably 
precedes a rounding off of the same region, though this extreme effect of senility 
was not observed. ‘The pile often cross the abdomen in the young, but not 
in the adult. In one specimen, however, which had the senile angularity of 
the abdomen well marked at the diameter of 73 mm., the pile again crossed 
the abdomen, and then faded out almost entirely. Another specimen, even at 
the extreme diameter of 105 mm., retained a keel, as in the adult. 
igoc. Beicheri, Wright, from the Angulatus bed, may be an example of this 
species. It exhibits the squared or quadragonal form of this series, and is not, 
as figured, at all similar to any species of the first subseries. oe. intermedium, 
Wright, from the lower part of the Angulatus bed, probably also belongs to 
* Quenstedt figures and describes, in his Amm. Schwab. Jura, one old specimen a trifle larger than that 
described above, which confirms this supposition as to the senile degradation of the keel, and it has no pile 
on the last whorl. The living chamber is still incomplete, though as long as the last volution. 
