﻿2 



DR. A. SMITH WOODWARD ON" 



[vol. lxxii, 



account of the shortness of the portions preserved ; but, as the 

 anterior ends suddenly begin to taper and eventually become very 

 slender, they are probably the pterygo-quadrates of the upper jaw. 

 The cartilage is •well calcified in very small tesserse, and, as shown 

 both by the portions of jaws themselves and by remains in front 

 of the fossil, the calcification penetrates more deeply than is usual 

 in recent Elasmobranchs. The best-preserved outer surface of 

 the cartilage, on the side of the specimen not shown in the figure, 

 is slightly marked with scattered fine pittings, such as have already 

 been described in Mdestus mirus. 1 



The row of fused symphysial teeth (s) of the Edestus type is 

 bilaterally symmetrical, and arched almost in the form of a semi- 

 circle. The eight teeth of which it is composed do not increase 

 much in size backwards, and' the depth of each crown slightly 

 exceeds twice that of its root. The crown is laterally compressed 

 and triangular in shape, much deeper than wide, with the sharp 

 anterior and posterior edges nearly straight, and the postero-inferior 

 angles much produced into slender, pointed extensions, which clasp 

 the next following tooth about as far as the posterior edge of its 

 crown. The superficial gano-dentine is smooth, but the base of the 

 crown is impressed irregularly with a few large vertical plications 

 or flutings, which are deepest in the anterior half and gradually 

 disappear in the posterior extension. There is also a faint longi- 

 tudinal median ridge on part of this extension. The anterior and 

 posterior edges of the crown are coarsely serrated, the serrations 

 (PI. I, fig. 7) being about 30 -in number on each edge, bluntly 

 rounded (not crenulated), and those in the apical portion inclined 

 upwards. In most of the teeth, however, the serrations are much 

 worn by an apparently single row of opposing teeth. They are 

 especially worn in the foremost tooth, irregularly on its anterior 

 edge, most deeply in the lower half of its posterior edge. The 

 wear is nearly similar in the second, third, and fourth teeth ; while 

 in the fifth and sixth teeth a large worn hollow (to) is conspicuous 

 in the upper half of the posterior edge. The apical portion of 

 the seventh tooth is unfortunately lost, but the eighth tooth is 

 complete and unworn, displaying all the serrations as previously 

 described. The separate tooth {t*) behind is crushed at the base, 

 and thus was probably not completely developed ; but the crown 

 exhibits well its smooth face and unworn serrated edges. It may 

 be either a ninth tooth of the series displayed or one of the 

 opposing dentition, which is otherwise represented only by a 

 broken fragment of one tooth in the edge of the shaly matrix of 

 the fossil. 



The root of the fused sjanphysial teeth is well seen in front, 

 where it has been extricated from the matrix, but it becomes 

 vague behind where the teeth were in process of formation. In 

 side view (PI. I, fig. 1) the limits of the successive conrponents 

 are Only just distinguishable ; but in lower view (PI. I, fig. 2) 



1 O. P. Hay, Proc. U.S. Nat. Mus. vol. xlii (1912) p. 32. 



