Annals of the Transvaal Museum 
31 
on both sides of the keel. The keel is sharp, and where its edge is still pro- 
tected by matrix it is even as sharp as a knife. A portion of the mouth-edge 
of the left side is preserved. This edge is slightly convex forwards at the 
umbilicus, concave forwards near the middle of the flank and again convex 
forwards at about one-third of the height from the periphery. 
The ornamentation consists of folds, spiral lines and growth-lines. Although 
the spiral lines and growth-lines are plainly visible, the details of this ornamen- 
tation cannot be given with absolute certainty, for the shell has been reduced 
to such thinness by weathering, that portions of sutures are visible everywhere. 
As far as can be made out, the spiral lines form a broad zone, which is situated 
on the inner portion of the outer half of the flanks. These lines are extremely 
shallow grooves, which are separated by broad and very slightly convex inter- 
spaces. In the type specimen growth-lines are only visible on one side of the 
beginning of the last whorl, and that from the umbilicus till past the middle 
of the flanks. This portion of the growth-lines has the same shape as the 
preserved portion of the mouth-edge. Growth-lines are preserved on a portion 
of another specimen, from the umbilicus till near the keel, the inner portion 
having practically the same shape as the preserved part of the mouth-edge 
of the type. The forward convexity, which in the type lies at about one-third 
of the height from the periphery, is here situated very near to the middle of 
the flank. From the convexity outwards the growth-line is strongly concave 
forwards. It is still concave forwards where it dies out close to the keel. 
Apparently, therefore, the keel was drawn forwards into a point. 
The flanks are covered by numerous more or less radial undulations. These 
undulations are practically invisible near the umbilicus, become more con- 
spicuous on the middle of the flanks, and quite prominent on the outer half 
of the flanks. On the inner portion of the flanks they are directed outwards 
and forwards, and on the outer portion outwards and backwards, so that they 
form a rounded angle near the middle of the flanks. Sometimes a short undula- 
tion is intercalated between two long ones on the outer portion of the flanks. 
Such a short one may unite with the long one posterior to it before reaching 
the middle of the flank, and the point of conjunction may be more prominent 
than the rest of the undulation. All undulation disappears on reaching the keel. 
The lobe-hne is very interesting. The external lobe is broad and deep, and 
divided by a very broad and very short siphonal saddle. It sends a secondary 
lobe backwards and inwards alongside of the siphonal saddle and another 
secondary lobe backwards and inwards into the body of the flrst lateral saddle, 
about in the middle of its length. These two secondary lobes are very conspicuous 
in all our specimens of Pelecodiscus. The flrst lateral lobe, which is long and of 
moderate breadth, is nearly as long as the external lobe, the last reaching 
slightly further backwards. This is taken with regard to a straight line through 
the centre of the umbilicus and the top of the siphonal saddle. The second 
lateral lobe is very broad and long. It has the same length as the external 
lobe and it reaches just as far backwards. Along its outline are many secondary 
lobes and saddles, arranged apparently without system. The third lateral lobe 
is short and moderately broad. It is about half as long as the second lateral 
lobe and reaches about half as far backwards. In the type it is trifld, but in 
the two other specimens it is irregular. The fourth lateral lobe is shorter than 
the third, but practically of the same breadth; it reaches slightly further 
backwards. In the type it is trifld, but in another specimen bifld. The fifth 
lateral lobe is greatly covered by the umbilical growth; it is very near to the 
umbilical edge of the shell. All that can be made out is, that it is very much 
shorter than the fourth lateral lobe. 
