On Cretaceous Cephalopoda from Znl/ihunl. 247 



crenulated keel of certain Upper Chico forms that cannot safely be 

 referred to such known genera as Muniericeras or Barroisiceras, and 

 probably are later than either. 



Locality. Umkwelaue Hill. Coll. Dr. A. L. du Toit. 



FAMILY : PLACENTICERATID^. 



GEN. PLACENTICEEAS, Meek. 



11. PLACENTICERAS SUBKAFFRAKIUM, sp. nov. 



(PI. XXI, figs. 2a-d.) 



This species is based on a fairly well-preserved specimen (No. 5106) 

 of the following dimensions : 



Diameter . . .85 mm. 



Height of last whorl . 50 per cent, of the diameter 



Thickness . 37 ,, 



Umbilicus . . .15 ,, ,, 



About one-half of the outer whorl belongs to the body-chamber, 

 but the mouth-border is not preserved. The suture-line given in 

 Fig. 2 d was taken at the beginning of the last whorl. 



The species differs from P. kaffrarium, R. Etheridge fil.,* in having 

 a smaller umbilicus (surrounded by tubercles that are very prominent 

 already on the inner whorls, as shown in the umbilicus), in having a 

 wider ventral area, and in the great thickness, caused by the prominent 

 umbilical tubercles. The very conspicuous lateral ribs of P. liaffrarium, 

 on the other hand, are not found in the example here described, but 

 it should be mentioned that near the end of the specimen, where the 

 shell has been removed, the lateral folds are more distinct on the 

 internal cast than they are on the shell. The latter only shows very 

 indistinct ribbing between the seven umbilical tubercles and the 

 twenty-eight elongated outer prominences (unpaired) that border 

 the flat and smooth ventral area. In addition to this distant ribbing, 

 there are fine sigmoidal striae, both on the shell, as in P. tamulicum 

 (Blauford) Kossmat,f and on the cast of the body-chamber, as in 

 P. stantoni, var. bolli, Hyatt. J. 



P. tamulicum, which, like the present species, belongs to the group 

 of P. syrtale, Morton, is distinguished from the form here described 



* Loc. cit. (1904, Second Report), p. 89, pi. iii, fig. 16. 

 t Loc. cit. (1895), p. 174, pi. xxii (viii), figs. 1 a-c. 



" Pseudoceratites of the Cretaceous," ' Mon. U.S. Ueol. Sui-v./ vol. xliv 

 (1903), pi. xli, fig. 7, p. 214. 



