Annals of the Transvaal Museum 
13 
lateral lobe is beautifully bifid. The second lateral lobe can only be regarded 
as trifid. The secondary saddle, which could have been the median one, if the 
lobe had been bifid, stands on the external side of the axis of the lobe and is 
directed forwards and inwards. There are five auxiliary saddles and six 
auxiliary lobes. 
Measurements : 
Type Paratype 
Diameter 
33-5 mm. 
(i-oo) 
Probably about 50 mm. 
Height of last whorl ... 
i6*7 „ 
(0-50) 
26 „ 
Thickness of last whorl 
17-1 » 
( 0 - 51 ) 
, 27-5 mm. 
Height of penultimate whorl ... 
6 „ 
(o-i8) 
Thickness of penultimate whorl 
7*5 ,, 
(0-22) 
Diameter of umbilicus ... 
7'3 » 
(0-22) 
The new form differs from Tetragonites superstes in the lobe-line, the shape 
of the whorls and the increase in size of the whorls. It is also easily distinguished 
from T. Timotheanus. There is much greater resemblance with T. epigonus. 
However, our form differs from this species in the shape of the whorls, the 
increase in size of the whorls, the ornamentation and the lack of constrictions 
and in the lobe-line. Some differences in the lobe-line have already been 
mentioned. Another difference with the type is the trifidity of the second 
lateral lobe. This trifidity is, however, also very pronounced in the lobe-line 
figured by Pervinquiere of specimens from Tunis (18, p. 76). 
This species is based on one beautifully preserved specimen and on an 
excellent fragment. 
Tetragonites nuperus n.sp. PI. Ill, figs. 3, 4, text-fig. 8. 
Shell discoidal, umbilicated, consisting of numerous whorls. Whorls in- 
creasing slowly in size, and slightly thicker than high. Greatest thickness 
between the middle of the flanks and the umbilical edge. External surface 
convex; flanks also convex, but convexity diminishing towards the umbilicus; 
near the umbilical edge the flanks are nearly flat. There is no demarcation 
between the external surface and the flanks. The umbilical surface is nearly 
vertical to the plane of symmetry and of moderate height. The umbilical 
surface passes very abruptly into the flank, thus forming a rounded umbilical 
edge. Involution one-third. Umbilicus large. 
The ornamentation of the shell is very delicate; it has mostly disappeared 
through decortication. The umbilical surface is covered with very fine ribs 
which are only visible with the help of a magnifying glass. They start vertically 
on the umbilical suture, but they very soon commence to lean forwards and 
they pass over the umbilical edge in a strongly forward direction. On the 
flanks and on the external surface they are represented by very fine growth- 
lines and grooves, which have the same direction as the old mouth-edges. 
Very slight spiral ridges are visible on the cast of the outer portion of the flank. 
I did not find indications of these ridges on the preserved portions of the shell 
of the type, but they are present on a preserved portion of the shell of para- 
type No. I. 
Old mouth-edges are not only visible on the last whorl of the type, but 
also on all the other specimens. Even the smallest shows a mouth-edge at a 
radius of 5 mm. They are less conspicuous or totally invisible on the earlier 
whorls of the type. They start at the umbilical suture leaning very slightly 
forwards, and they pass over the umbilical edge in a strongly forward direction. 
The whole of the mouth-edge on the flanks is slightly convex forwards. This 
convexity is retained on passing on to the external surface. The mouth-edge 
