G. C. Crick — On Ammonites calcar. 



555 



British Museum (Natural History) that were also obtained from 

 Dr. Bruckmann. The fact that the " species " is very rare and that 

 this specimen has been labelled, "■Am. calcar, Zieten (unique)," and 

 marked " Zieten coll.," at once suggested a comparison of the 

 example with Zieten's figure. So exactly did it agree with Zieten's 

 figure that I was led to enquire whether Zieten's type-specimen was 

 known to exist elsewhere. 



Fig. 1. — Zieten's type-specimen of Aitimoiiites calcar [= a deformed example of 

 BonareJIia bicostata, Stahl, sp.]. a, lateral view ; b, front view, showing the 

 single row of tubercles on tlie periphery and the asymmetry of the septal 

 surface ; c, peripheral vieAV, showing the single row of tubercles near the 

 centre of the periphery ; d, suture-line, the dotted line near the middle 

 indicating the position of the single row of tubercles, and the short curved 

 lines at each end marking the position of the suture of the shell. Brown 

 Jura {■ (Lower Oxfordian) : Gammelshausen, near Boll, Wiirttemberg. 

 Drawn of about twice the natural size, from the specimen in the British 

 Museinn (Natural History) collection [37,670]. 



In one of his papers on " The Fossil Cephalopods of the Museum 

 of Comparative Zoology," ^ at Harvard College, Cambridge, Mass., 

 Professor Hyatt refers to "specimens from Zieten's former collection," 

 which were sent to that Museum by the Museum of Stuttgart. 



Eeplying to my enquiries, Dr. E. Fraas, of Stuttgart, very kindly 

 informs me that there are only a few of Zieten's type-specimens at 

 Stuttgart, that the type-specimen of Ammonites calcar is not among^ 

 them, and that the large collection there does not contain a single 

 specimen that can be referred to that ' species.' He also states that 

 he does not consider Ammonites calcar to be a distinct species, but 

 a deformed example of some other species, possibly of Ammonites 

 bipartitus. 



Professor Koken, of Tubingen, tells me that, with few exceptions, 



1 Bull. Mus. Comp. Zool., vol. i (1864-9), p. 79. 



