434 Professor H. G. Seeley—New Cape Labyrinthodont. 
The transverse sections, back and front, are vertical and clean, 
practically unworn, and of similar transversely oblong form. 
In the middle is an oblong central cavity (M.), which is less than 
an inch wide and less than half an inch deep. From it the sutures 
radiate which separate the constituent bones. When the specimen is 
examined from the external surface the only well-marked sutures are 
upon the base, so that on such evidence the jaw might be interpreted 
as formed of two bones. The narrow straight lateral line between the 
surangular and splenial on the inner side might pass for a crack 
in the specimen. Similarly, the line in the external groove between 
the elements of the dentary and infra-dentary might have been 
supposed to be the opposite side of the same fracture but for the 
transverse sections. These lateral conditions are found to be natural 
divisions when the broken ends of the fragment are examined. More 
or less serrated and angulated sutures are marked by lines of black 
matrix as represented in the figure (see Pl. XIX, Fig. 1). They 
are not all followed with equal facility, and the external dentary bone 
is obscurely divided into superior and: inferior elements by suture, for 
the division is less evident at the other fractured end. The com- 
plicated suture between the internal splint bone, which I regard as 
the splenial, and the two bones on which it rests is also less distinct 
on the posterior fracture in this specimen, where the surface is more 
weathered, but may be followed with a magnifying-glass. The most 
interesting suture is the vertical division, showing that two distinct 
parallel bones support the teeth in two parallel rows, of which the 
outer row is rather the longer. 
The external dentary bone carries five teeth, which are close set. 
Their crowns are broken and show no trace of a pulp cavity. The 
basal attachment is four times as wide as long from front to back. 
The attachment of the teeth is of a pleurodont type, for the external 
alveolar border rises fully half an inch above the rounded internal 
exposures of the crowns; and on their inner side the dentary bone rises 
as an oblique rounded strip from the groove in which these teeth are 
imbedded. Both front and back fractures pass through the bases of 
crowns of teeth. In the middle of the base of the tooth, on what may 
be the posterior fracture, the crown descends in a small short oblong 
portion into a shallow socket, and shows the same folded structure as 
the rest of the tooth. The smooth surfaces of the teeth are marked 
with fine parallel vertical grooves upon the enamel, which vary in 
depth on the several teeth. Each crown decreases in size as it 
ascends, by becoming narrower from within outward. 
The bone which abuts against the dentary above the Meckelian 
vacuity on the inner side of the jaw is regarded as the surangular 
bone, and. beneath it is the angular bone. The lateral junction 
between these bones is hidden by the splint-like covering of the 
splenial. The determination of these elements rests upon the sutures 
shown in the transverse sections. But if there is an infra-dentary, 
there may also be an infra-angular ; and these elements may be upper 
and lower divisions of the angular bone. 
The upper or surangular bone is small compared with the dentary, 
to which it is parallel and internal. At its suture with the dentary 
