On Cretaceous Cephalopoda from ZuJnJcnid. 315 



is found again. The inner whorls of the present example, however, 

 show that the resemblance with certain Acanthoceraticls, notably 

 Calycoceras naviculare, Mantell sp.* is quite superficial. 



The Persian example of " Acanthoceras cornueli" recorded by H. 

 Douvilk't is much more coarsely costate than the specimen here 

 described. 



The very large Douvilleiceras, referred to on pp. 220 and 303 as 

 coming from the South Branch of the Manuan Creek, belongs to a 

 different group of forms. It somewhat resembles the large (and more 

 rapidly increasing) " P achy discus " Waageni, Antlmla.t in its closely 

 costate outer whorl, but appears to be a development of the Albiau 

 mammillatum group (as far as can be judged by the poorly preserved 

 younger whorls), and possibly is a very large example of the form 

 figured by Etheridge. It does not appear to have anything to do 

 with the Aptian form here described. 



* Also recorded from Madagascar, though the two forms figured by Boule, 

 Lemoine and Thevenin (loc. cit., 1907, p. 30, pi. viii, figs. 1 and 2) are very 

 doubtful. Fig. 2 may be a Mantelliceras, with smooth ventral area on the 

 inner whorls, whereas Ca/i/coceras, which is a post-Melacantkoplites stock, has a 

 median row of tubercles in the young. In Calycoceras gentoni (Brongniart = 

 Sharpe's figs. 3 and 5, pi. xviii) all the ventral tubercles disappear at about the 

 same time (' Pal. Univ.,' 191 1, No. 223) ; in C. naviculare, Mantell sp. (lectotype, 

 Sharpe's figs. 1 and 8, pi. xviii (B.M. No. 36834), Mantell's original being useless), 

 the two ventro-lateral rows persist longer than the median row. Mantell's type, 

 refigured in a posthumous paper by Crick (" A. uavicularis, Mantell," ' Proc. 

 Mai. Soc.,' vol. xiii, 1919, pp. 154-160, pi. iv) is too worn and scraped'abotit to 

 show any tubercles, and the writer believes that what Crick (p. 157) had 

 considered as differences of specific value cannot be relied on, some of the ribs 

 being artificially carved, or at least scraped, and the original shape of the whorl 

 is quite unrecognisable. The resemblance to the Indian and Portuguese forms, 

 which are very tumid-whorled, and to d'Orbigny's figure may not be so great 

 as appears from a comparison of the figures, and in India, as in the English 

 Chalk, a number of undescribed forms of Calycoceras occur ; for Stoliczka 

 (p. 74) states that " there are specimens which have scarcely any trace of either 

 lateral or dorsal tubercles, even in the youngest stages," i. e. forms near to 

 C. ba//lei, Pervinquiere (= A. sarihacense, Bayle). Peron and Pervinquiere had 

 drawn attention to the similarity between Calycoceras of the Cenomanian and 

 the Turonian Fagesia. Crick (in coll.) had labelled Mantell's type " Fagesia 

 navicnlaris," but since he did not refer to this genus in his last paper, he 

 probably came to the conclusion that the specimen, after all, was a Cenomanian 

 " Acanthoceras" as he did in his earlier work on the False Bay fauna (p. 205). 



t " Mission Scientif. Perse, Morgan," vol. iii, " Et. Geol., ' pt, iv, ' Pal.,' 1904, 

 p. 231, pi. xxviii, figs. 1 a, I/. 



Loc. cit., p. 10(5, pi. ix, figs. 1 a, b, Sinzow {loc. cit., 1900), p. 164, pi. i, 

 fig. 10 (as Douoilleieeras mei/endorffi, var. waageni). 



Loc. cit. (Third Report), pi. v, fig. 1. There also is a resemblance to 

 Choffat's Acanthoceras marques-costai (' Conducia,' 1903, p. 27, pi. vii, fig. 2), 

 but this form is compared with Cenomanian Ammonites. 



