36 
Annals of the Transvaal Museum 
appeared in larger specimens. In all three types the relative height of the 
last whorl decreases with advancing age, while at the same time the relative 
diameter of the umbilicus increases. 
The flanks are covered by growth-lines, which are slightly concave forwards 
near the umbilicus, strongly convex forwards on or near the middle of the 
flanks and strongly concave forwards in their outer half. In young specimens 
this is practically the only ornamentation of the flanks. Sometimes, however, 
the surface of the flanks has a wavy appearance through the possession of 
extremely low and broad ribs and interspaces, which have the same course as 
the growth-hnes. These waves are generally less conspicuous on the inner 
portion than on the outer portion of the flanks. They are sometimes so clear, 
that some of them are seen to originate at the umbilical tubercles, while others 
apparently only start on the middle of the flanks. These ribs may be very 
conspicuous at the shoulder near the keel, but they do not cut this shoulder 
up into tubercles. 
Large specimens show broad, shallow constrictions on the cast, probably 
old mouth-edges. They have the same shape as the growth-lines. On the outer 
surface of the shell these old mouth-edges are represented by a thickened rib,, 
which seems to border the groove on the cast behind. 
The lobe-line differs from that given by Baily and by Griesbach, Baily’s 
figure being nearly correct. The first lateral lobe is longer than the external 
lobe and stands obhquely on the axis of the lobe-line. The first lateral and the 
auxiliary lobes are trifid. The second lateral lobe is irregular, all its secondary 
lobes having more or less the same length. The external lobe is broad. The 
external saddle and the first lateral saddle are practically of the same length. 
The second lateral saddle is small and forms with the four auxiliary saddles 
Text-fig. i8. Schloenbachia U mhulazi y 3 x . 
GriesbacM . Lobe-line of para type from 
dorsal to ventral line, on a radius of 
about 13 mm. X3. «=umbilical su- 
ture; &= umbilical edge. 
a series, which gradually diminishes in height. There are five auxiliary lobes, 
which gradually diminish in length towards the umbilicus. The axis of the 
lobe-line is practically straight. The internal portion of the lobe-line has been 
developed in a small specimen. There are five internal saddles, which gradually 
diminish in height from the antisiphonal lobe towards the umbilical suture. 
There are also five internal lobes, which obey the same law. The antisiphonal 
lobe is narrow and longer than any of the five internal lobes. 
Measurements : 
Type 
Diameter ... 
95*5 mm. 
(i-oo) 
69’5 mm. 
(I-OO) 
47*7 mm. 
(I-oo) 
Height of last whorl 
45 
(0-47) 
35-2 „ 
(0-51) 
25-6 „ 
(0-54) 
Thickness of last whorl . . . 
21*7 ,, 
(0-23) 
15 
(0-22) 
II-7 » 
(0-25) 
Height of penult, whorl ... 
24-6 ,, 
(0-26) 
16-9 „ 
(0-24) 
10-6 „ 
(0-22) 
Thickness of penult, whorl 
19 
(0*20) 
I3-I » 
(0-19) 
57 »» 
(0-12) 
Diameter of umbilicus . . . 
16-9 „ 
(o-i8) 
10 ,, 
(0-14) 
6-6 „ 
(0-14) 
Text-fig. 17. Schloenbachia Umbulazi 
var. Gviesbachi. Lobe-line of para- 
type up to the umbilical suture on 
a radius of 16 mm. x 3. 
