232 Annals of the South African Museum. 



The shell is partly preserved and 3 mm. thick in places, but 

 less than 2 mm. in others. It is in two thick layers, fibrous and of 

 a white porcellauous aspect, like certain Inoceramus shells in the 

 chalk, with a thin inner and outer coating. The specimen may belong 

 to a fat form of ParapacJiydiscus, like the two examples previously 

 described, but is too incomplete for specific determination. The large 

 ParapacJiydiscus from Pondoland are far more compressed. 



Locality. Lake Itesa (Eteza), Umfolozi. Coll. "W. J. Wybergh. 



FAMILY : PRIONOTROPID.E. 

 GEN. MORTONICERAS, Meek. 



5. MORTONICERAS WOODSI, Sp. 110V. 



(PI. XXI, figs. 1 a-fZ.) 



The single specimen (No. 5451) upon which this species is based 

 has the following dimensions : 



Diameter . . . . .80 mm. 



Height of the last whorl . . 45 per cent, of the diameter. 



Thickness ,, ,, . . 40 ,, ,, 



Umbilicus . . . . . ? 25 



The important characteristics of this new species are (1) the decline 

 of lateral and peripheral ornament on the last whorl, which is still 

 septate, so that the specimen represents the inner whorls of an 

 Ammonite that appears to lose altogether the typical Mortoniceras 

 features ; (2) the projection of the tubercle at the overhanging 

 umbilical edge in an inward, not a lateral direction ; (3) a com- 

 paratively small umbilicus. 



Among a large number of Morton In- rax of the type of M. soutoni 

 (Baily)* from the Umtamvuua River, in the British Museum, there 

 are some transitional forms to the present species, showing decline 

 of tuberculatiou on the outer whorl (at a cousidei-ably larger diameter) 

 and a decrease in the size of the umbilicus. On the other hand, one 

 of the forms figured by Stuart Wellerf as Mortoniceras delawarense, 



* The example figured by Woods (loc cit., 1906, p. 337, pi. xliii, fig. 1 ) repre- 

 sents a more evolute shell. Baily's type in the British Museum (Geol. Soc. 

 Colin. No. 11365) has the decline of tuberculation more pronounced, but at a 

 diameter of close on half a metre is still costate. Its small umbilicus brings 

 it closer to the new species here described than is Woods' more evolute 

 example. 



t "Keport on Cret. Pal. of New Jersey," vol. iv (Pal. Ser.), 'Geol. Surv. of 

 New Jersey,' 1907, p. 837, pi. civ, figs. 1-3 only. (See under Mortoniceras 

 Vanuxemi, Morton sp., p. 308.) 



