182 GENESIS OF THE ARIETIDAL. 
Schlotheimia Charmassei, Wiuvyer. 
Summ. Pl. XI. Fig. 5. 
Amm. Charmassei, D’OrB., Terr. Jurass, Ceph., p. 296, pl. xci. (not pl. xcii.). 
Amm. angulatus compressus, QuENST., Amm. Schwab. Jura, pl. ii. fig. 2. 
Amm. angulatus compressus gigas, QUENST., Ibid., pl. iv. fig. 2. 
Schlot. Charmassei, Wiu., Unt. Lias, Mojsis. et Neum., Beitr., IV. p. 196. 
4igoc. Charmassei, Wriaut, Lias Amm., p. 823, pl. xx. fig. 1-3. 
Localities. —Semur, Lyme Regis, Tiibingen, 
Besides the characteristics mentioned in the description of angulata the follow- 
ing may be added. On the sixth volution, the extremely gibbous form of the 
young begins to change. The whorl increases more rapidly, the abdomen is 
narrower, and the pile as in preceding species, with this exception. On this 
volution, or perhaps on the fifth, they become bifurcated, or else have interme- 
diate short pile interspersed between the longer ones. The sutures have remark- 
ably large abdominal lobes, shallower than the superior laterals, but with much 
more ragged outlines. The siphonal saddle is extraordinary in this respect. It _ 
is very large, and marked with several lateral minor lobes and saddles. The 
remaining lobes and saddles are more complicated than in angulata. 
On the sixth volution, the form of the whorl changes more than in angulata. 
The involution of this whorl equals one half of the side of the sixth, whereas in 
angulata the envelopment does not equal this until it reaches the ninth volution. 
The involution at the same age in this species, i. e. on the ninth whorl, covers 
full two thirds of the side of the eighth whorl. ‘There is a form in Professor 
Fraas’s collection from Méhringen answering to the young of Charmassei, as fig- 
ured by D’Orbigny, Plate XCI., and another from Filder, which is precisely inter- 
mediate in its characteristics between this and the smoother, flatter variety figured 
on Plate XCII. The oldest specimens in the possession of the Museum of Stutt- 
gardt measured 53 mm., and the last whorl 23 mm. Schlot. angulala parts with its 
pile and grows smooth much earlier apparently than Charmassei. Possibly this 
occurs at about the same age, but the superior size of Charmassec makes it seem 
older when the senile characteristics begin to appear. 
Schlotheimia Leigneletii, Winner. 
Amm. Leigneletii, D’Ors., Terr. Jurass. Ceph., p. 298, pl. xcii. 
Schlot. Leignelelii, Wku., Unt. Lias, Mojsis. et Neum., Beitr., IV. p. 197. 
Amm. compressus (pars), QUENST. 
Localities. —St. Thibault, Semur, Vaihingen, Stuttgardt, Behla. 
The same class of facts divides this species from Charmasset that we used 
above to show the differences between the latter and angulata; namely, that the 
young differ as well as the old in some specimens. 
The differences are very great between the fifth whorl of Leigneletii, and the 
same age in Charmassei. The tubercles are more prominent on the edge of the 
abdomen, the pilze more depressed on the sides, and their terminations tubercular 
on the edge of the abdomen, which, instead of being a broad, rounded space, is a 
