lii 
CRETACEOUS BRACIIIOrODA 
time in doubt whether there existed suOiciout reason for separating both specifically. 
However, the constant very small size of the beak in the Indian form, as observed in 
several hnndreds of specimens, from at least a dozen of different localities and from 
distinct beds, appears to me to indicate the validity of a species distinct from the 
European fossil. During the process of growtli the shell is subject to a very large 
amount of variation, which will he better understood by an inspection of the figures, 
than by a lengthened description. In all cases, however, is the shell broader than 
long, unless it be due to an accidental deformity. Young specimens arc often very 
fiat, only with an indication of the frontal sinus. In growing larger cither the 
breadth or the convexity of the A’alves increases at a greater ratio, and, according to 
this, varies also the depth and widtli of the frontal sinus, Avhich sometimes is very 
abrupt. The haemal valve is always considerably more convex than the neural one, 
Avhich is only slightly tumid towards the beak, but not to the same extent as usually 
seen in specimens of plicatUis. 
Equally variable, as is the form, is also the ornamentation. When the surface 
is well preserved, the ribs always show some kind of a scaly crcnidation, which is 
produced by then.' being abruptly intersected or crossed by lines of growth, and at 
each such intersection the edges of the ribs arc sharply turned upwards. 
In younger specimens these lines of growth are sometimes almost as numerous 
as in B. crenifem, in others they are more distant, but in older specimens there 
are generally only two to four of them present towards the margin of the valves, 
and the rihs, unless very avcU preserved, arc mostly smooth. Among several 
hundred specimens I only found one which has the radiating ribs rather strong 
and about 31 in number. A few specimens from the same bed and locality, and 
also some others have about 50 radiating ribs. But in the majority the n um ber is 
about GO, in some it rises as high as 80, and in one large one from Anapaudy I 
counted 90. A comparatively greater number of specimens belonging to the pre- 
sent species is much more finely ribljcd than the Eiwopean pUcatilis. 
An inrportant distinction of plicatiloides is, as already observed, the small size 
of the beak, the beak ridges being ahvays conspicuously concave and just visible 
in a luemal view of the shell ; very rarely arc their edges sharp, and the area be- 
tween tlicm and the hinge-line on cither side is about three quarters of a millimeter 
broad. 
The beak ridges meet at an angle varying from 115° to 135°. The cardinal 
teeth of the neui-al valve are thin, but long ; the bi'achial apophyses of the hmmal 
valve are, as usually, turned upwards, somewhat broader at their ends, and on the 
inner side provided with a shallow groove. Both, hinge-teeth and the apophyses, 
arc comparatively closer together than in B. plicatilis. 
Jjocdlilies. — Shalanure, in earthy ferruginous beds, at the base of the Trichi- 
nopoly group, very common ; Audoor, south-west of Veragoor, Kullajq south-west 
of Koloturc, Kolakonuttom, &c., (all in Trichinopoly group) ; Ootacoil, common ; 
Olapaudy, Comarapolliam, Kampaudy, Shillagoody, &c. (Arrialoor group). 
