Annals of the Transvaal Museum 
II 
visible on about half of the last whorl. The complete living-chamber of the 
type-specimen, the first complete one known of Tetvagonites, occupies three- 
fourths of the last whorl. The smallest specimen of the three is also complete 
and its living-chamber may also extend over three-fourths of the last whorl. 
The lobe-line is essentially that of 
Tetvagonites Timotheanus Mayor sp. The 
saddles diminish in size from the external 
one inwards. The lobe-line is built on a 
nearly straight axis, that is to say, the 
umbilical portion of the lobe-line only 
runs very slightly backwards. The external 
saddle and both lateral saddles are trifid. 
The lobes are fairly broad. The external 
lobe is slightly longer than the first lateral 
one; the lobes become gradually shorter 
towards the umbilical suture. There are four auxiliary lobes. 
Measurements : 
Type Paratype 
Diameter 
40 mm. 
(i-oo) 
32-4 mm. 
(I-OO) 
Height of last whorl ... 
17-3 » 
(0*43) 
I4’2 ,, 
( 0 - 44 ) 
Thickness of last whorl 
i8-2 „ 
(0-46) 
15-5 » 
(0-48) 
Height of penultimate whorl 
9-3 » 
(0-23) 
7-2 „ 
(o-22) 
Thickness of penultimate whorl 
9-5 » 
(0-24) 
8-3 ,, 
(0-26) 
Diameter of umbilicus 
10-4 ,, 
(0-26) 
8*3 .. 
(0-26) 
The present species shows great 
resemblance to both 
Tetvagonites Timothe- 
anus Mayor sp. and Tetvagonites epigonus Kossmat. The lobe-line, as far as 
visible, is very much like that of T. Timotheanus. In T. Timotheanus, however, 
there are two auxiliary saddles and possibly a minute third one, while in the 
new form there are three auxiliary saddles and a minute fourth one. Further, 
in T. Timotheanus the first auxiliary saddle lies on the edge of the umbilicus, 
while in T. supevstes the second auxiliary saddle lies external to or on the 
umbilical edge. The whorls of T. Timotheanus have a somewhat different shape 
and are relatively thicker than those of the new form. No mention has ever 
been made of spiral ridges on T. Timotheanus-, these ridges are visible even on 
the cast of the new form, and would, therefore, also have been noticed on casts 
of T. Timotheanus if this species had spiral ridges. I take it, therefore, that 
this is another difference between the two forms. 
The lobe-line of the present form differs from that of T. epigonus in the 
fact, that the umbilical portion of the suture only runs very slightly backwards. 
The first lateral lobe is also relatively broader. The shape of the whorls is 
different in the two forms and no spiral ridges have been observed in T. 
epigonus. The mouth-edges of both T. Timotheanus and T. epigonus are more 
convex forwards near the external surface than in T. supevstes. The only other 
species as far as I know, with ridges or lines, is Tetvagonites sphaevonotus Jimbo 
sp. It appears from Jimbo’s (11, p. 35, PI. VI, figs. 3, 4) and Yabe’s ( 15 , Pt i, 
p. 45, PI. VII, fig. i) description, that this species has rounder whorls, and 
Yabe's figures show the mouth-edges to have a different shape. 
Four specimens have been found, one of which has been chosen as the 
type; two others are well preserved, but the fourth is in bad condition. 
Tetragonites virgulatus n.sp. PI. Ill, figs, i, 2, text-fig. 7. 
Shell discoidal, umbilicated, consisting of a few thick whorls. Whorls 
broader than high. Greatest thickness at or slightly internal to the middle of 
the flanks. Sides of whorl and external surface convex. The last whorl shows 
Text-fig. 6. Tetvagonites supevstes. 
Lobe-line of type up to near the 
umbilical suture on a radius of 
13 mm. X 3. 
