70 Transactions of the Boyal Society of South Africa. 
are finest on the umbonal area but afterwards coarser with age, and 
divided into more or less regular groups according to the periodical 
growth-lines of the shell ; the posterior area is covered with closely 
arranged oblique striations forming angulations at the ridge as they 
pass over from the anterior face. Hinge area wide with a strong 
dentition, possessing in the left valve a massive central cardinal 
tooth, united at the base by a stout nearly horizontal fulcrum to the 
succeeding anterior tooth, and divided from the latter by deep and 
comparatively narrow sockets ; between the posterior (only slightly 
indicated) and middle cardinal tooth is a deep and more or less 
trigonal socket ; a large smooth excavation, representing the position 
of the adductor muscle, occurs at the imperfect end of hinge area. 
Dimensions (left valve). — 
Length (about) 100 mm. 
Height „ 90 „ 
Umbonal ridge (length) 160 ,, 
Posterior area (width) 35 ,, 
Thickness of shell structure beneath the anterior 
end of hinge region 15 
Observations. — The specimen described is of fragmentary cha- 
racter, retaining parts of both valves, although only the left has been 
selected for characterisation on account of the right valve being 
mostly in the condition of an internal cast. The form is evidently 
closely allied to F. forhesiana, but differs in its larger and more 
ponderous size, and its more massive hinge area ; the sculpture is 
more regular, the elevated lamelliform costae being absent ; and 
further, the umbonal ridge is more obtuse. The valves are slightly 
open, showing the anterior dental character of the left valve, the 
incurved summits being about 15 mm. apart. The major part of the 
right valve is represented by an internal cast, showing a narrow, 
elongate, and rounded umbonal area with a lengthy and spreading 
ventral region, besides large adductor scar markings and pallial line, 
which are well impressed. 
There is a second specimen representing the exterior of a left valve 
of medium size, measuring about 70 mm. in both directions, which 
most probably belongs to this species, but it is so imperfect in the 
ventral direction and so covered with matrix, that some uncertainty 
exists as to its identification. The prominent umbo-ventral ridge is, 
however, present together with the partly preserved posterior area, 
which is very abrupt and of considerable depth. Some similarity is 
also seen between this specimen and Veniella (?) sanctce-luciensis, of 
E. Etheridge, jun., from the Umsinene Eiver deposit of Zululand (in 
Mr. Anderson's " Third and Final Eeport of the Geological Survey of 
