‘f 
GILMORE: OSTEOLOGY OF BAPTANODON (MARSH) 99 
absence in previously discovered specimens. The English form Ophthalmosaurus 
icenicus shows about the same peculiarity in the retention of the teeth. Baur® has 
observed small teeth at the end of the jaws of the (Baptanodontidee) Ophthalmosawrus 
contained in the private collection of Mr. Leeds in Peterborough, England. Lydek- 
ker™ also speaks of alveoli being present at the end of the jaw in this genus, although 
the groove is known to extend posteriorly. 
In the jaws of No. 878, although the alveolar channels are better preserved than 
in specimen No. 603, there was not even a fragment of a tooth recovered, but we have 
evidence of their existence at one time in the faint alveolar partitions preserved on 
the inner wall of the right dental groove. (See Pl. VIII.) 
As suggested in a preliminary paper in Science the final exhumation of the jaws 
of No. 603 revealed more teeth, nine in all, six of which were in the groove of the 
upper jaw, the remaining three being attached by matrix to the 
alveolar surface of the lower mandible. With but one exception 
all of the teeth were lying prone upon the surfaces of the grooves. 
The largest and best preserved tooth found was cemented to the 
lower jaw by the matrix just anterior to the forward extremity of 
the left maxillary. The tooth as preserved (see fig. 6) measures 29 
mm. in length, and undoubtedly represents the teeth of the pos- 
terior part of the series. The base (see fig. 7) is somewhat anguiar 
in cross section, but as the tooth rises it becomes more 
rounded ending in a circular subacute apex. There is 
no swelling of the base as may be observed in the teeth 
Fia. 6. Poste- 
rior tooth of Bapta- 
of many of the Ichthyosawrs. A little more than the en a 
nies cna eUPbes third is covered with enamel which is impressed Gross _ sec- 
603). Twicenatural with fine longitudinal strize, between which are interven- tion of the 
i 7 : 5 6 0 same tooth 
size. The transverse ing depressions. ‘These grooves begin quite abruptly at 
fracture represents (No. 603). 
the point at whicn the base of the enameled surface and extend upward, Nearly 
the cross section was gradually subsiding before reaching the apex which is twice nat 
gree smooth. A cross section near the mid portion of the oie 
cement covered base shows the tooth to have a somewhat flattened periphery at 
either end of the line of its greatest diameter. Considering these surfaces as the 
contact between the tooth and the outer and inner walls of the dentary groove, the 
tooth would curve in slightly. But it is hard to understand how the shallow and 
widely separated walls of this groove could ever have been in apposition with the 
ch) Baur, lit. cit. 
34 Lydekker, R., ‘* Catalogue of Fossil Reptilia and Amphibia in the British Museum.’’ 
