EASTMAN: FOSSIL LEPIDOSTEIDS. ri! 
are crushed into a confused mass. The outer rim of the dentary is set with 
a series of numerous minute teeth, next to which is placed a single series 
of large conical teeth implanted vertically in a narrow and moderately deep 
longitudinal groove. There are nine of these teeth spaced at regular intervals 
from the symphysis to about the middle of the lower jaw. They are of nearly 
uniform size, about 2 cm. in height, and vertically striated. Coronal cross- 
sections show the complicated structure of dentine characteristic of the genus. 
The symphysial teeth are directed forwards at a slight angle. The symphyses 
of both rami lie contiguous to one another in the limestone, but by far the 
greater portion of the left mandibular ramus and whole of the left maxillary 
are concealed by overlying bones. 
Next above the right maxillary lie a pair of long and narrow, deeply chan- 
nelled or folded elements, which presumably represent the palatines ; and 
adjacent to these are the median series of bones belonging to the cranial roof, 
which are now laterally displaced and very considerably injured. The oblique 
sutures between the frontals and ethmonasals are well shown, and also the 
sutures along the median line of the head. Premaxillaries and nasals are not 
preserved, and most of the bones belonging to the otic and occipital region are 
either missing or crushed beyond recognition. For this reason the length of 
the head in the median line cannot be accurately determined, although a con- 
servative estimate would place it at about 40cm. The distance in a straight 
line from the symphysis of the lower jaw to the posterior margin of the oper- 
culum is 45cm. The right and left clavicle are partially visible behind the 
head, but are in nowise remarkable either in size or configuration. 
Fins. — Very little remains of either of the pectorals, but all the remain- 
ing fins are beautifully preserved. The dorsal and anal are triangular, broad- 
based, and relatively high (20-22 cm.), with eight dermal rays each. These fins 
are very remote, and nearly opposed to each other. The caudal has a length 
of 24 cm., is composed of twelve finely articulated long rays and a lesser num- 
ber of short rays which differ from the rest in being uniserially articulated 
throughout their length. Prominent biserial fulera fringe the dorsal and 
ventral margins of the caudal and front margins of the remaining fins. The 
extreme tip of the tail is nof preserved, but it was apparently very slightly 
rounded. The pelvic fins are situated about midway between the pectorals and 
anal, and resemble the latter in form and size. 
The long proximal joints of each dermal ray in all the fins consist of two 
halves, or right and left portions, rather loosely united along the axial plane, 
and consequently subject to displacement. These proximal pieces correspond 
in number to the interneurals, which likewise have suffered some displacement 
in the dorsal and pelvic fins. Immediately after the proximal joint the rays in 
all fins become biserially articulated, and after a short interval become further 
bifurcated, much like the arms of crinoids. It will be seen from the following 
table that little variation in the radial formula exists amongst the various 
living and fossil species : — 
