Annals of the Transvaal Museum 
35 
Genus SCHLOENBACHIA Neumayr emend, de Grossouvre. 
Schloenhachia Umhulazi Baily sp. 
1855. Ammonites Umhulazi Baily, 3 , p. 456, PI. XI, fig. 4. 
1871. Ammonites Umhulazi Griesbach, 5, p. 63, PI. Ill, fig. i. 
1904- Muniericeras {?) Umhulazi Solger, 16, p. 205. 
1906. Schloenhachia Umhulazi Woods, 17, p. 336. 
This species is remarkable for its variability, ranging from smooth to ribbed 
and tuberculated specimens. This inconstancy is not apparent from Baily's 
original description, nor from that of Griesbach and Woods. However, a 
slight indication of the presence of variation is given by the two last mentioned 
investigators, where they both state that the ribs are not so prominent as they 
appear to be in Baily’s figure. Woods states that the type cannot be found, 
and therefore this judgment is based on evidence from other material. 
I have now before me about 230 specimens of this species. There are 
amongst this lot specimens which agree more or less with the type, and others 
which are just hke the specimen figured by Griesbach. It has been possible 
to arrange them into three series, two of which agree more or less with the 
specimens of Baily and Griesbach. Those agreeing with Baily’s figures are 
by no means the most numerous, but, because of their agreement with the 
type, they will be taken as typical forms. The specimens agreeing with 
Griesbach’s figure are regarded as a variety, which is named after Griesbach, 
who was the first to figure one of its representatives. The third series is a 
variety with still coarser tubercles and ribs than those of the typical form and 
will therefore be appropriately called var. spinifera. 
Schloenhachia Umhulazi Baily sp. var. Grieshachi n. var. PI. VII, figs. 3, 4, 
PI. VIII, figs. I — 5, text-figs. 17, 18. 
Shell discoidal, umbilicated. Whorls strongly involute, high and narrow. 
Greatest thickness in young specimens near the umbilical edge ; with advancing 
age the greatest thickness may wander to near the middle of the flanks, and 
in large specimens the greatest thickness lies actually in that position. The 
lateral surface of the whorls is slightly convex in very young shells. It is very 
soon divided into two portions by an extremely low and broad ridge, situated 
at or slightly internal to the middle of the flanks. This ridge often develops, 
especially in larger shells, into a broad, slightly convex zone. In the early 
stages the inner portion of the surface is flat and that of the one side is 
practically parallel with that of the other. In later stages the inner portions 
of the two surfaces diverge slightly outwards and in large shells these portions 
are also slightly concave. The outer portion of the flanks is practically flat; 
sometimes it is very slightly convex and sometimes even very slightly concave. 
Very young shells have no keel; the external surface is then smooth and evenly 
and strongly convex, the keel only commencing at a diameter of about i cm. 
In the smaller specimens this keel is nothing else but the sharp edge in which 
the flanks meet, but in the largest specimen it is a high and narrow crest. 
Soon after the commencement of the keel a shoulder is formed on the flanks, 
very close to the keel. In large shells this shoulder is less pronounced than in 
younger ones and on the last whorl of our largest specimen it has practically 
become a strongly convex portion of the flank. The umbilical edge is smooth 
in very young specimens. In practically all the specimens of medium size the 
edge of the umbihcus bears a row of tubercles. These do not start at a fixed 
period for they are present in fairly small shells, while they have not yet 
3—2 
