132 PSEUDOCERATITES OF THE CRETACEOUS. 
species. It has the narrow, deep, smooth ventral channel, which is also 
shown in Uhlig’s figure, with the same peculiar abrupt ventral terminations 
to the costae with forward bend on the edge of the channel. The venter is 
not cut up into waves by the crossing of the coste as in H. pulchelliformis. 
The channel, in fact, is deeper than the depressions between the coste, and 
the ridges that guard it on either ridge give a pointed aspect to the forward 
terminations of the costz. This is also observable in Uhlig’s figure. 
On splitting this specimen I succeeded in exposing three substages 
of neanic age. The first substage showed famt costz that crossed the 
rounded venter, the form being at this time rounded, with gibbous sides and 
open umbilicus. Then faint tubercles appeared, the venter still remaining 
rounded between them. These tubercles in the next substage became more 
prominent, and the venter between them became flattened. The cost 
became more prominent at the same time on the outer half of the side and 
made a slight forward bend on to the venter. Soon after this a very faint, 
narrow, linear depression indicated the beginning of the ventral channel. 
I was not able to discover at what age the second range of tubercles began 
to come in nor their exact position. The volution is gibbous on the sides 
throughout these early stages and is a rather stout young form with an open 
umbilicus. 
Locality: Escragnolles, France. 
Age: Barremian. | 
HEINZIA MATURA n. sp. Hyatt. 
Pl. XV, figs. 12-18. 
This species is allied to that described above by Sayn. It is similar 
in its compressed form, in the amount of involution and in the broad 
ventral channel, and in having a row of tubercles on the umbilical shoul- 
ders. The costz are, however, much broader and have the double external 
termination of the group of Heinzia. This termination is, however, not 
distinguishable on the earliest part of the outer volution, but is well devel- 
oped on the third quarter of this volution. This termination is seen in this 
specimen to be a modification of the ends of the costze, and it is not due to 
the approximation and coalescence of an inner row of tubercles with the 
outer row. The shell is preserved on one side of this specimen and shows 
