6 
Annals of the Transvaal Museum 
The ribs are for a short distance perpendicular to the umbilical suture. 
They then bend strongly forwards, which direction changes gradually to 
nearly radial on the middle of the flanks ; further outwards the ribs again bend 
forwards to form a broad and very short, tongue-shaped, forward convexity 
on the external surface. 
There are four old mouth-edges on the last whorl, which follow the same 
course as the ribs, and which present themselves as a sulcus bordered behind 
by a thick, broad rib. 
The lobe-line is typically that of Gaudryceras. The external lobe is very 
narrow and longer than the first lateral lobe. 
It is symmetrically divided by a very narrow 
siphonal saddle, the anterior end of which nearly 
reaches the radius through the anterior end of 
the secondary saddle in the first lateral lobe. 
The external saddle and both lateral saddles 
are more or less s^^mmetrically divided by a 
secondary lobe. There are four auxiliary saddles 
at the end of the last whorl. From the first 
lateral saddle the lobe-line runs backwards and 
inwards and the radius of its crossing point with 
the umbilical suture lies behind that of the 
posterior end of the external lobe. The second 
lateral lobe stands obliquely, that is to say, is directed forwards and inwards. 
Measurements : 
Text-fig. 2. Gaudryceras tenui- 
lineatum. Lobe-line of type 
up to the umbilical suture on 
a radius of 14 mm. x 3-4. 
Diameter 
Height of last whorl ... 
Thickness of last whorl 
Height of penultimate whorl . . . 
Thickness of penultimate whorl 
Diameter of umbilicus... 
26-5 mm. (i-oo) 
7-3 „ (0*28) 
10-8 ,, (0-41) 
4*3 ,, (o-i6) 
7-6 „ (0-29) 
13*4 „ (0-51) 
If the last whorl were removed, the shell would have a diameter of 15 mm. 
or at the most 16 mm. The relative dimensions would then be: 
Diameter 
Height of last whorl . . . 
Thickness of last whorl 
Diameter of umbilicus 
15 mm. (i*oo) 
4-3 » ( 0 - 29 ) 
7 - 6 „ (0-51) 
8- 6 „ (0-57) 
16 mm. (i-oo) 
4-3 ,, (0-27) 
7- 6 „ (0-47) 
8- 6 „ (0-54) 
This new species differs from Gaudryceras Sacya Forbes sp. by the shape 
of its whorls. In the young stages the whorls of G. Sacya are round, according 
to Kossmat and Stoliczka, while the whorls of G. tenuilineatum are much 
broader than high. The whorls of Gaudryceras muUiplexum Kossmat have a 
different shape and the ornam.entation of this species is much coarser. The 
young whorls of G. varagurense Kossmat have a different shape and the 
ornamentation of this species is also coarser. There is great resemblance be- 
tween G. tenuilineatum and G. subtililineatum Kossmat. The whorls of both 
increase slowly in size and are much broader than high; the involution is in 
both species the same and the sculpture of both is invisible to the naked eye. 
The difference between the two forms lies in the fact, that the whorls of 
G. subtililineatum increase quicker in size than those of the African form. This 
difference is apparent when the specimen of G. tenuilineatum is compared with 
Kossmat’s figure of G. subtililineatum (12, PI. XIX, fig. 2). If our form at 
a diameter of 15 to 16 mm. is compared with the measurements of a specimen 
of G. subtililineatum of the same diameter, it will be seen that the whorls of 
