Annals of the Transvaal Museum 
7 
our form are relatively thicker. These differences made it necessary to keep 
the two forms separate. However, there is still some doubt, caused by the 
impossibility of comparing the two forms in all characters. The state of 
preservation of the known specimens of G. subtililineatum was apparently such, 
that not all the characters of the species could be studied. The sculpture of all 
other species seems to be coarser. Gaudryceras Kayei Forbes sp. differs also 
in the relations of its whorls at comparable stages. The whorls of Gaudryceras 
valudayurense Kossmat increase much quicker in size than those of our form. 
Only one specimen of this species has been found. 
Gaudryceras varicostatum n.sp. PI. II, figs. lo — 12, text-figs. 3, 4. 
Shell discoidal. Whorls broader than high, but the height increasing more 
rapidly than the breadth. Greatest thickness at the umbilical edge. The sides 
of the whorl round off evenly into the peripheral surface; they also round off 
into the umbilical surface, that is to say, there is no real umbilical edge, the 
surface is only more convex in this region. This shape of whorl is present even 
in the youngest whorls visible, from a diameter of 5 mm. upwards. External 
surface of older whorls broadly convex, of last whorl narrower and more convex. 
Lateral surface of last whorl less convex than of preceding whorls. Umbilical 
surface of last whorl steeper than of the preceding whorls. Involution moderate. 
The last whorl embraces less than two-fifths of the height of the preceding one. 
Umbilicus large. 
The ornamentation of the shell varies from the umbilicus outwards. The 
umbilical surface is covered with fine, wire-like ribs, which mostly start at 
the umbilical suture and which pass on to the flank. Some of them, on the 
older whorls, do not start at the umbilical suture, but slightly away from it. 
At the middle of the flank these ribs flatten out and nearly disappear. On the 
older whorls it is seen, that the flattening begins just before the ribs are covered 
by the next whorl. Some of the ribs bifurcate before reaching this point. At 
the end of the last whorl these wire-like ribs cover the flank completely and 
they only leave a comparatively narrow peripheral surface for the hair-ribs. 
Where the ribs are flattened out they correspond with three, four or five finer 
ribs, which can only just be seen with the naked eye. Most of these finer ribs 
start at the extreme end of the coarser ones, but some are intercalated between 
them. They are very short, in fact, they do not get out of the zone of the 
umbilical suture. To the naked eye the external surface seems to be smooth. 
This, however, is not so, for with a glass magnifying about ten times one can 
clearly see, that it is covered with numerous, close-set, extremely fine ribs. On 
the external surface of the last whorl these ribs have been removed by weather- 
ing. On the beginning of the last whorl there are about 100 of these ribs to 
a chord of i cm. Opposite the place where these were counted there were 
about 28 coarse ribs at the umbilical suture on a chord of the same length. 
Starting from the umbilical suture the coarse ribs are directed slightly 
forwards and in passing on to the flank they bend more forwards. They are 
therefore concave towards the front. On the flank the coarse ribs and the 
short flank-ribs are slightly convex forwards. The very fine ribs are slightly 
concave forwards at their beginning on the flank and rather strongly convex 
forwards on the external surface. 
There are four sulci on the last whorl, which follow the same course as the 
ribs. These sulci are bordered behind by a thickening of the shell. 
The lobe-line is typically that of the genus Gaudryceras. The external lobe 
is narrow and has the same length as the first lateral lobe. It is symmetrically 
divided by a narrow siphonal saddle, which is not longer than the secondary 
