EASTMAN: FOSSIL LEPIDOSTEIDS. 71 



arc 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 40 cm. The distance in a straight 

 line from the symphysis of the lower jaw to the posterior margin of the oper- 

 culum is 45 cm. 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 s<hort rays which differ from the rest in being uniserially articulated 

 throughout their length. Prominent biserial fulcra fringe the dorsal and 

 ventral margins of the caudal and front margins of the remaining fins. The 

 extreme tip of the tail is not 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 intemeurals, 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 

 li\nng and fossil species : — 



