On Cretaceous Cephalopoda from Znluland. 313 



A specimen (No. 5117) of 72 mm. diameter, with only the body- 

 chamber portion (occupying three-quarters of a whorl) well preserved, 

 and with the inner whorls largely replaced by crystalline calcite, has 

 the following proportions : 



Height of the last whorl . 38 per cent, of the diameter 

 Thickness ,, . 47 ,, 



Umbilicus . .35 ,, ,, 



The coronatiform innermost whorls (diameter = 4 mm.) have a 

 depressed whorl-section with prominent lateral spines and constrictions, 

 like the ammonite next described, and like Cheloniceras royerianutn, 

 d'Orbigiiy sp. The following stage, represented by Krenkel's figures, 

 and comparable with Sinzow's examples of Cli. seminodosum (Sinzow) 

 and Cli. meyendorjfi (d'Orbigny),* is badly pi'eserved. Only the first 

 prominent rib, at the beginning of the well-preserved body-chamber 

 portion, has a lateral tubercle, in addition to the umbilical one, so that 

 there is loss of the characteristic bituberculation, as stated by Kreukel, 

 and as shown in the specimen of "D. cornuelianum " figured by Kilian.f 

 The latter, however, has lost the umbilical tubercle, as well as the 

 lateral one, whereas in the form here described this umbilical tubercle 

 remains distinct on some of the longer ribs, which feature approaches 

 the present example to Ch. albrechti-austriae (Hohenegger), Sinzow 

 sp.,+ to Cli. tschernyscheivi, var. laticosta, Siuzow sp., and to other 

 forms of the cornuelianum group. || 



On account of the imperfect condition of the present example,^ 

 identification with Kiliau's form, or with any of the other species of 

 the cornuelianum group, is, perhaps, impossible, but though Cli. 

 yottscJiei, was only figured in small examples, it appears probable that 

 the pi-eseut specimen represents the adult stage of that form, showing 

 "decline" of the costation, as does Ch. meyendorffi (d'Orbigny) in 

 Sinzow.** The present example, at any rate, is closer to the 



* " Besclir. einiger Douvitleiceras-A.T:ten a. d. Ob. Neocom. Hussl.," ' Verh. 

 Euss. Kais. Min. Ges.' (ser. 2), vol. xliv (1906), pi. i, figs. 6 and 8. 



t Loc. cit. (1913), p. 339, pi. ix, fig. 3. 



I Loc. cit. (1906), pi. iv, figs. 1 and 2, and Kilian, loc. cit. (1913), pi. viii.fig. 2. 



Ibid., p. 187, pi. iii, fig. 1, and Kilian, loc. cit. (1913), p. 340, pi. ix, fig. 5. 



|| A specimen in the British Museiim (No. 46590), from the Isle of Wight, is 

 almost indistinguisable from the present form in ornament and suture-line, 

 but the whorl- section increases more rapidly in width. 



If The restoration of the inner whorl, given in fig. 1 c, is somewhat problem- 

 atical. Only two or three ribs are shown (on one side only), and of these one 

 has the inner, the other only the outer, tubercle preserved. 



** Loc. cit. (1906), pi. i, fig. 8. 



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