THIRD, OR VERMICERAN BRANCH. 141 



Caloceras laqueum, Hyatt. 



Summ. PI. XI. Fig. 32. 



.4mm. laqueus, Qdenst., Amm. Schwab. Jura, pi. xviii. fig. 4; pi. i. fig. 14 (not fig. 15, 16). 



Amm. intermedium, Portl., Geol. Londonderry, p. 136, fig- 17. 



JEgoceras intermedium, Weight, Lias Amm., p. 314, pi. xv. fig. 3, 4 (not fig. 5, 6). 



Mgoceras Belcheri, Weight, Ibid., p. 313, pi. xv. fig. 7-9 (not pi. xix. fig. 1, 2). 



Ariel. Scylla, Wah., Unt. Lias, Mojsis. et Neuin., Beitr., VI 1387, pi. xxv. fig. 7, 8. 



Amm. Scylla (pars), Reynes, 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 pilse evidently 

 began early, and were closely crowded and slightly curved forwards. 



In one specimen the pilce 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. 1 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. Johnstoni and those of 

 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 45 mm. 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 Cal. Johnstoni. The sutures also 

 vary in the same way, some specimens having sutures like those of Johnstoni, and 

 others approximate to those of carusense and spiratissimum. 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 pike 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 pilas 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. 



jEgoc. Belcheri, 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. JEgoc. intermedium, 

 Wright, from the lower part of the Angulatus bed, probably also belongs to 



1 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 pila; 

 on the last whorl. The living chamber is still incomplete, though as long-as the last volution. 



