562 G. C. Crick — Zieten's Types of Ammonites. 



of Zieten's types; these are the type-specimens of (i) Ammonites 

 polygonius and (ii) Ammonites discoides} 



(i) Ammonites pohjgonius, C. H. v. Zieten, Verstein. Wiirttembergs, 

 Heft iii (1831), p. 21, pi. xv, figs. 6a, b, c. This specimen [register 

 number 39,699] is labelled in Dr. Bruckmann's handwriting as 

 follows : " Ammonites pustulatus Suevicus, Quenst. (Amm. polygonius, 

 Ziet.) Selten. Brauner Jura ^ (Ornatenthon), Gammelshausen"; and 

 on the label there has been written in pencil the letters " [Dr. 0.]," 

 signifying " Dr. Oppel," as I have been able to ascertain from other 

 labels in this Museum that are also in Dr. Bruckmann's handwriting. 

 The s^Decimen agrees so well in size, form, and colour with Zieten's 

 figure (except that the latter is reversed), that there cannot be any 

 doubt whatever about its being the type-specimen, the imperfection 

 of the anterior part of the fossil being accurately represented in 

 Zieten's fig. 6a. The periphery, however, is not so sharp as Zieten's 

 fig. 6b indicates, but is slightly truncated^ owing to the absence of 

 the keel. The specimen is entirely septate, but the suture-line is 

 only imperfectly displayed ; its complete course cannot be traced. 



Zieten described the species as follows : — " Eticken scharf, die 

 sehr dicken, der Liinge nach feingestreiften Windungen bilden einen 

 tiefen Nabel, welcher mit spitzigen Knotchen umgeben ist. Eippen 

 theils einfach, theils gegabelt. Nach dem vieleckigen Durchschnitt 

 seiner Windungen benannt. Verkiest im Lias-Schiefer von Zell, 

 unweit Boll." 



["Back (periphery) sharp; the very thick longitudinally finely-striated whorls 

 form a deep umbilicus, which is surrounded by pointed tubercles. Eibs sometimes 

 simple, sometimes bifurcated. Named after the polygonal shape of the cross-section 

 of its whorls. Pyritized in the Lias shales of ZeU, not far from BoU."] 



From the above remarks it will be seen that Zieten's statement as 

 to the horizon and locality does not agree with the label which now 

 accompanies the specimen, for the fossil is labelled " Brauner Jura tf 

 (Ornatenthon), Gammelshausen," which is a short distance south-east 

 of Boll, in Wiirttemberg, whilst Zieten states that the species 

 occurred in the "Lias-Schiefer von Zell," i.e., a little to the north- 

 east of Boll. According to Oppel (" Juraformation," p. 560), the 

 species occurs pyritized in the "Zone of Ammonites anceps" [ = the 

 Brauner Jura f in part] at Oberlenningen and Gammelshausen, near 

 Boll ; and Quenstedt, in his work on " Die Ammoniten des schwab- 

 ischen Jura " (Bd. ii. Heft 14-15, 1887, p. 755, tab. Ixxxvi, fig. 10), 

 describes and figures the species, under the name Ammonites pustu- 

 latus suevicus, from the Brauner Jura ^ of Gammelshausen. It is 

 most probable, then, that the specimen is accurately labelled ; for it 

 is quite evident that some other species which Zieten attributed to 

 the Lias are certainly not of Liassic age. 



It may be mentioned that this species has been referred ^ to Denys 



1 Briefly alluded to in Geol. Mag., December, 1899, p. 556, note 1. 

 - See F. A. Quenstedt's "Die Ammoniten des schwiibischen Jura," Bd. ii. 

 Heft 14-15 (1887), tab. Ixxxvi, fig. 10. 

 3 See "Waagen's " Jurassic Fauna of Kutch," vol. i (Cephalopoda), 1873, p. 41. 



