HYL^^OBATIS. 19 



Family Myliobatid.e (?). 



Genus HYLiEOBATIS, novum. 



Generic Characters. — Teeth more or less transversely elongated, with truncated 

 ends, the crown overhanging the root on all borders. Oral surface of crown gently 

 tumid, sloping down to its low and rounded anterior border, but sharply separated 

 behind from a deep and concave posterior surface ; covered with enamel which is 

 variously marked with wrinkles. 



Type Species. — Hylxohatis jjroblematica, described below. 



Bemarks. — This genus is known only by a few small isolated teeth evidently of 

 one species, and its afl&nities are uncertain. The teeth must have been arranged 

 in a close tessellated pavement, as in the Cretaceous Ptyckodus and the Tertiary 

 Myliobatid skates. The slight bevelling of their ends shows that they alternated 

 in transverse series ; and occasional pressure-scars denote crowding. The super- 

 ficial wrinkling of the enamel is rather suggestive of the rugosity round the margin 

 of some teeth of Ptychodus ; the deep concave posterior face of the crown and the 

 low rounded anterior border also recall corresponding features in the same 

 Cretaceous teeth. It may even be added that their microscopical structure (Text- 

 fig. 10) agrees with that of the teeth of Ptychodus (Text-fig. 11) though there is 

 nothing in this to distinguish them definitely from Cestraciont teeth. It is thus 

 possible that Hylseobatis may prove to be one of the long-sought forerunners of 

 Pfychodiis. 



1. Hylaeobatis problematica, sp. nov. Plate V, figs. 1 — 5; Text-fig. 10. 



Type. — Tooth without root ; York Museum. 



Specific C]iaracters.—The type species, founded on isolated teeth measuring 

 from 6 to 13 mm. in longest (transverse) diameter. Oral surface of dental crown 

 feebly marked with coarse vermiculating wrinkles, which are more or less reticulate 

 and pass at the front border into stronger vertical wrinkles ; concave posterior 

 face smooth or marked with slight vertical flutings ; the anterior and posterior 

 borders nearly straight and nearly parallel. 



Description of Specimens. — The type tooth from Brook (PL V, fig. 1) lacks the 

 root, but is otherwise well preserved. It is not bilaterally symmetrical, one end 

 being wider and deeper than the other and distinctly bevelled for contact with two 

 teeth. Its oral surface (fig. 1) is gently tumid, a httle worn during life in its 

 hinder half, but well preserved laterally and anteriorly, and feebly marked with 



