On Cretaceous Cephalopoda from Zululand. '277 



FAMILY : DIPOLOCERATID^B. 

 GEN. DIPOLOCEKAS, Hyatt. 



4. DlPOLOCERAS CRISTATUM, Deluc sp. 



(PI. XXV, fig. 2 ; PI. XXVI, fig. 6.) 



1822. Amm. cristatus, Deluc in Brongniart. Environs de Paris, 

 pp. 95 and 395, pi. vii, fig. 9. 



1907. Mortoniceras (/) cristatum (Deluc), Pervinquicre. Et. d. Pal. 

 Tunis. Ceph. Ter. Second, p. 239. 



1908. Mortoniceras (7) cristatum (Deluc), Jacob. " Et. Pal. and Strat 

 Part. Moy. Ter. Oct.," Trav. Lai). Grol. Univ. Grenoble, vol. viii. 

 pp. 326 and 384. 



This well-known species is represented in the collection by two 

 examples of the following dimensions : 



No. 2728. No. 2727. 



Diameter . 144 mm. 65 mm. 



Height of last whorl . 35 per cent. 33 per cent. 



Thickness (at promi- 

 nent costae) . ? 40 44 



Umbilicus . 39 40 



There is particularly good agreement with the coarse form figured 

 by Brouguiart. The keel is narrowed at its base, like that of the form 

 described below as D. sp. nov. or of Ooster's A. roissyanus (d'Orbigny) 

 varietas.* The extremely pronounced forward sweep of the costation, 

 near the end of the large example (see fig. 2, PL XXV), is particularly 

 striking. This probably represents the mouth border with its rostrum, 

 but unfortunately the latter is not perfectly preserved. f The length 

 of the body-chamber is well over half a whorl ; the last few (approxi- 

 mate) suture-lines are very simple but could not be exposed sufficiently 

 well for complete delineation. What can be seen differs from the 

 suture-line figured by PictetJ (fig. 5 c) in having shorter and wider 

 elements and from that of fig. 2 f in having simpler outlines. The 

 internal portion shows part of the dorsal saddle, but the antisiphonal 

 lobe is hidden by matrix that did not permit of further preparation. 



* ' Catal. Ceph. Foss., etc.,' I860, iv, p. 144, pi. xxvi, figs. 6 and 7. 



t d'Orbigny's figure (/oc. i-if., pi. Ixxxviii, fig. 1) probably is restored and 

 composite, for according to the evidence of the example here described, the 

 curve of the costae near the end is quite different, and all tuberculation has 

 disappeared. 



I In Pictet & Koux, ' Moll. Foss. Ores. Verts./ 1847, pi. viii. 



