SECOND, OR SCHLOTHEIMIAN BRANCH. 133 



flattened zone. The reduction of the abdomen of course occurs in all species of 

 this group, but in other species, except Boucaultiana, it is found only during the 

 senile stage. 



Amm. angulatus compressus of Quenstedt may also in part belong to Charmassei, 

 since two specimens from the Stuttgardt Museum of this name apparently belong 

 to this species only. The envelopment in one of these specimens covers about 

 two thirds of the sides of the eighth whorl, and about the same age the pilse 

 again cross the narrow abdomen, obliterating the median depression or smooth 

 zone, and introducing a series of crenulations instead. This is a return to the 

 young condition, and indicates the first degradational or clinologic stage. It is 

 not intended by this to deny that there are no young which closely approximate 

 to the young of Charmassei. On the contrary, some specimens are apparently 

 identical in all respects, except the greater flatness of the whorls and the earlier 

 period at which involution appears, and the two species are connected by numer- 

 ous transitional forms. 



Sehlotheimia Boucaultiana, Wahner. 



Siimm. PI. XI. Fig. 6. 



Amm. Boucaultianus, D'Orb., Terr. Jurass. Ceph., p. 294, pi. xo. 



Schlol. Boucaultiana, Wah., Unt. Lias, Mojsis. et Neum., Beitr., IV. p. 196. 



JEgoc. Boucaultiana, Wright, Lias Amm., p. 327, pi. xviii. fig. 1-4. 



Locality. — Semur. 



This remarkable species differs from Leigneletii in about the same manner that 

 the latter differs from Charmassei, in other words, it is more involute than Leigne- 

 letii at the same age ; i. e. on about the seventh or eighth whorl at least three 

 fourths of the sides are hidden. The pilae are not so coarse as in that species, 

 and the abdominal channel is obliterated at an earlier age and is succeeded by 

 crenulations caused by the pilse. The sutures differ considerably. The specimen 

 examined was one of D'Orbigny's types. The same transitional forms which lead 

 into Leigneletii also lead into other more compressed and more involute forms 

 which are transitional to the true Boucaultiana. They differ from Leigneletii only 

 in the suppression of the tuberculated pilae, and a general tendency toward obso- 

 lescence of the pilae on the sides. 



Schlotheimia D'Orbignyana, Hyatt. 



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

 Locality. — Semur. 



This species has depressed pilae and resembles closely Boucaultiana, but is not 

 so involute. It is in fact, as described by D'Orbigny, an extreme modification of 

 Charmassei, with excessively compressed whorls, and acquiring in the clinologic 

 stage a subacute abdomen. It resembles more closely Schlot. ventricosa of Wahner 

 than it does any other species, but it is even more compressed and more like 

 Charmassei in the adult stage than that species. D'Orbigny's figure is that of an 

 old shell ; the adults are less acute and more like Charmassei or Leigneletii. 



