L32 GENESIS OF THE AK1ETID.E. 



Schlotheimia Charmassei, Wahner. 



Sumni. PI. XI. Fig. 5. 



Amm. Charmassei, D'Orb., Terr. Jurass. Ceph., p. 296, pi. xci. (not pi. xcii.). 

 Alum, angulatus compressus, Quenst., Amm. Schwab. Jura, pi, ii. fig 2. 

 Amm. angulatus compressus gigas, Quenst., Ibid., pi. iv. fig. 2. 

 Srhlol. Charmassei, Wah., Unt. Lias, Mojsis. et Neum., Beitr., IV. p. 196. 

 JEgoc. Charmassei, Wright, Lias Amm., p. 323, pi. xx. fig. 1-3. 

 Localities. — Semur, Lyme Regis, Tubingen. 



Besides the characteristics mentioned in the description of ungulata 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 pilae as in preceding species, with this exception. On this 

 volution, or perhaps on the fifth, tbey become .bifurcated, or else have interme- 

 diate short pilae 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 Mohringen 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. ScMot. angulata parts with its 

 pil33 and grows smooth much earlier apparently than Charmassei. Possibly this 

 occurs at about the same age, but the superior size of Charmassei makes it seem 

 older when the senile characteristics begin to appeal-. 



Schlotheimia Leigneletii, Wahner. 



Amm. Leigneletii, D'Orb., Terr. Jurass. Ceph., p. 298, pi. xcii. 



Scli/oi. Leigneletii, Wah., 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 Charmassei 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 pilae 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 



