144 
Annals of the Transvaal Museum 
The specimen is entirely septate. No species is known to me with which 
the new form could be confounded. Remarkable in the species, although by 
no means singular, is that the; breadth of the last whorl is relatively greater 
than that of the preceding one, and further the extraordinary height of the 
penultimate whorl with regard to its breadth. 
Tetragonites teres n.sp. PI. XXV, figs. 1, 2. 
Shell discoid al, umbilicated, with a few rapidly increasing whorls. Whorls 
higher than broad. Greatest thickness at the umbilical margin. Sides of whorl 
flat, becoming rounded towards the periphery. External surface strongly 
convex, rounding off gradually into the sides. Umbilical surface very steep. 
Inclusion two-thirds. The surface of the shell is smooth and covered with 
growth-lines, which are only visible with a magnifying glass. Two faint 
constrictions are visible, having the same shape as those of Tetragonites epi- 
gonum. Lobe-line very imperfectly known; as far as visible showing the 
general type of Tetragonites. 
Measurements : 
Diameter 
69 mm. (1) At diam. of 
57 mm - 
(1) 
Height of last whorl 
39 , 
. (°'57) 
3i - 
(o-54) 
Thickness of last whorl 
p 
26 ,, 
(0-46) 
Diameter of umbilicus 
14 , 
, (o-20) 
There is only one specimen upon which the above description has been 
based. About a quarter of its last whorl is probably body-chamber. The 
specimen has suffered somewhat from lateral compression. A portion of the 
last whorl, however, has not been compressed at all, and in this region the 
measurements on the diameter of 57 mm. have been taken. 
The new species differs from Tetragonites Timotheanum Mayor sp. and 
from T. epigonum Kossmat by the fact that its whorls are higher than broad ; 
in the two species mentioned they are broader than high. T. Timotheanum is 
also more involute and its whorls have an angular section. The section of the 
whorls of T. epigonum is also more trapezoidal than that of T. teres. The 
height of the last whorl is greater than half the diameter of the shell in the 
new species, whereas in T. Timotheanum it is equal to or, especially in T. epi- 
gonum and young specimens of T. Timotheanum, less than half this diameter. 
Holcodiscus Faku n.sp. PI. XXV, figs. 3, 4. PI. XXVI, figs. 1, 2. 
There are two specimens which are regarded as belonging here. The 
following description has been taken from the smaller of the two. 
Shell discoidal. Whorls higher than broad. Greatest thickness at the 
umbilical edge. Sides of whorl nearly flat near the umbilical margin, becoming 
more and more convex towards the periphery. External surface strongly 
convex. Umbilical surface low and very steep. Involution moderate, between 
one-half and two-thirds of the preceding whorl being embraced. 
Umbilical surface smooth. Sides of whorl covered with numerous, high 
and narrow ribs. All ribs pass with undiminished strength over the outer 
surface. The ribs emanate partly from strong, sharp, radially elongated 
tubercles, which have a flat and steep anterior surface and which stand on the 
extreme umbilical margin. The umbilical edge of these tubercles passes for 
a short distance on to the umbilical surface and stands practically perpen- 
dicular on the lateral edge of the protuberances. The ribs emanate from these 
tubercles in an irregular way. Sometimes the edge of one rib is continuous 
with the edge of the tubercle, while another rib emanates from its side. In 
other instances the edges of two ribs are continuous with the edge of the 
