■556 G, C. Crick — On Ammonites calcar. 



Zieten's originals are not in Tubingen, but that the collection there 

 contains the two examples of Ammonites calcar figured by Quenstedt. 

 According to Zieten's own statement on the title-page, the originals 

 of his " Versteinerungen Wiirtembergs " were in the collection of 

 Dr. Hartmann, in Goppingen, after whose death they passed, according 

 to Professor Koken, into the hands of Krantz, of Bonn. In all 

 probability, therefore, the specimens were dispersed, and we think 

 there can be no doubt whatever that the example now in the British 

 Museum collection is Zieten's type-specimen.' It must, however, 

 be pointed out that this example is labelled in Dr. Bruckmann's 

 handwriting, " Brauner Jura ^, Gamelshausen," whereas Zieten states 

 that this species came "aus dem untern Oolith bei Guttenberg." - 



A minute examination of the British Museum specimen — sub- 

 sequently referred to as Zieten's type-specimen — shows it to be 

 deformed. Firstly, the two branches of the siphonal lobe, instead of 

 being placed one on each side of the median line of the periphery, 

 are both on the left ^ side of the median row of tubercles, so that the 

 septum, when viewed from the front (see Fig. 16), is decidedly 

 unsymmetrical. Secondly, a close examination of the tubercles on 

 the periphery, especially of those near the anterior end of the 

 specimen, reveals an indication of subdivision in the median line, 

 as if each were formed by the coalescence of two antero-posteriorly 

 elongated tubercles. Further, the whole specimen is not quite 

 symmetrical, the left side of the whorl being a little more inflated 

 than the right, and the peripheral tubercles a little on one side of 

 the median line (see Fig. Ic). 



Quenstedt "^ regarded Zieten's Ammonites calcar as a deformed 

 example of Ammonites bipartitus, Zieten, and in this opinion was 

 supported by Bronn'^ and Oppel," for both these authors referred 

 Amm. calcar and Amm. bipartitus to the same species (Ammonites 

 hicostatus, Stahl), the last-named author adding in a parenthesis 

 after the reference to Amm. calcar the word ' Missbildung.' Giebel,^ 

 however, regarded Amm. calcar as a separate species, an opinion 

 which appears to be shared by Parona and Bonarelli.® 



On comparing Zieten's figure of Ammonites calcar with that of his 

 Amm. bipartitus a great similarity in the sculpture is at once 



1 This view is supported by the subsequent discovery in the Museum collection of 

 two more of Zieten's type-specimens {Ammonites discoides, p. 21, pi. xvi, figs, la, 

 ■h, c; and Ammonites polygonius, p. 21, pi. xv, figs. 6a, h, c), both of which were 

 obtained from Dr. Bruckmann. 



- The only place of this name in Wiirttemberg that the writer has been able to 

 find is about eight miles due east of Dettingen and is spelt ' Gutenberg.' Gammels- 

 hausen is near Boll, which is about nine miles north-east of Gutenberg. There is 

 also a discrepancy about the horizon and locality of the two other specimens in the 

 Museum collection that are believed to be Zieten's types. 



^ The terms ' right ' and ' left ' are used in a purely morphological sense. 



* F. A. Quenstedt: "Petref. Deutsch.," Bd. i, Cephalopoden (1846), p. 140; 

 and "Amm. Schwab Jura," Bd. ii (1887), p. 735. 



5 H. G. Bronn: Index palseont. , 1848, p. 33. 



^ A. Oppel: " Die Juraformation," 1856-58, p. 560 (1857). 



' C. G. Giebel: " Die Fauna der Vorwelt," 1852, p. 567. 



8 C. F. Parona & G. Bonarelli : Mem. Acad. Sci. Savoie, ser. 4, vol. vi, p. 141, 

 1897. 



