Annals of the Transvaal Museum 
33 
The. lobe-line shows great resemblance with that of P. umzambiensis. The 
external lobe is deep and moderately broad. This lobe has two secondary 
lobes on each side, as in P. umzambiensis . The first lateral lobe, which is long 
and narrow, is shorter than the external one, its length being about three- 
quarters that of the last. Its posterior end reaches just as far backwards as 
the anterior secondary lobe of the external lobe. The second lateral lobe is 
very long and narrow. It is just as long as the external lobe, but it does not 
reach as far backwards. Along its outline are many small, secondary lobes 
and saddles. The third lateral lobe is short and about as broad as the second. 
Its length is about half that of the second lateral lobe and it reaches about 
half as far backwards. The fourth lateral lobe is slightly shorter and narrower 
than the third and reaches much further backwards. Its posterior end occupies 
about the same level as the posterior end of the second lateral lobe. The fifth 
lateral lobe is shorter than the fourth and this is about all that can be made 
out of it. This lobe is situated very close to the umbilical edge. 
The two first lateral saddles are long and narrow. Secondary lobes cut 
deep into the body of the first one, but the second one is only fringed with 
small secondary lobes and saddles. The third lateral saddle is broader than 
the second. Both the second and the third lateral saddle are very superficially 
bifid, and the two arms of both saddles are even shallower bifid. The fourth 
lateral saddle is narrow and fairly long and bifidity is just indicated. The fifth 
lateral saddle is much shorter and also narrow; bifidity is just visible. 
Measurements : 
This species differs from the type of the genus and from Pelecodiscus 
Jullieni Pervinquiere sp. by its long and narrow saddles and lobes external 
to the third lateral saddle. The internal portion runs much stronger backwards 
than in either of the other species. However, the differences are best seen by 
comparing the figures. It differs further from P. umzambiensis in the possession 
of undulations around the umbilicus. 
Only one specimen of this species was found. 
Pelecodiscus amapondensis n.sp. PI. VII, figs, i, 2. 
Shell discoidal, with closed umbilicus. The umbilicus of the specimen is 
closed on one side, but not on the other. This seems to be an abnormal con- 
dition. It is supposed that the normal shell has a closed umbilicus at this stage. 
Whorls much higher than broad and increasing rapidly in size. Greatest thick- 
ness of last whorl situated at about one-quarter of the height of the whorl 
from the centre of the umbilicus. About three-quarters of a whorl earlier the 
greatest thickness lies very close to the centre of the umbilicus. The lateral 
surface of the whorl is convex where the shell is thickest. The left umbilicus 
is filled with shell-growth which is raised in the centre to a kind of process. 
Around this process lies a groove-like concavity. The lateral surface of the last 
whorl is only very slightly convex from where the shell is thickest towards 
the periphery. This portion of the lateral surface is actually flat at the be- 
ginning of the last whorl. Where the keel is preserved it is apparent that the 
lateral surfaces show practically no concavity along its sides. Only a small 
portion of the keel of the last whorl is preserved, and that at its beginning. 
This portion is blunt, broad and rounded, its thickness here being about 
2*5 mm. The keel of the preceding whorl, which is visible about half a volution 
earlier than the described blunt keel, is sharp. 
Diameter 
Height of last whorl . . . 
Thickness of last whorl 
about 53 mm. (i-oo) 
33 (0-62) 
13 (0-25) 
3 
