A. Smith Woodward — On the Genus Notidanus. 205 

 II. — On the Paleontology of the Selachian Genus Notidanus, 



CUVIER. 



By A. Smith "Woodward, F.G.S., 

 of the British Museum (Natural History). 



(PLATE VI.) 



AMONG the Selachians of the existing fauna, there are none of 

 greater interest and higher morphological importance than 

 Notidanus, Cestracion, and the recently-discovered Chlamydoselachus 

 from Japanese seas. These are the solitary survivors of once 

 nourishing types, whose immediate congeners are only known to 

 Biological science through the fragmentary remains preserved in the 

 geological record ; and the value of the archaic features they present 

 is even further enhanced by the slight information already acquired 

 regarding the geological distribution of their numerous extinct allies. 



Hitherto, however, there appears to have been no attempt at a 

 systematic treatment of the Paleontology of the first of these genera, 

 although the Cestraciont and Cladodont types have received a large 

 share of attention. I therefore propose to offer a short account of 

 the present state of knowledge of this subject — summarizing the 

 results of previous research, making known a few interesting fossils 

 that have not yet been described, and adding some general remarks 

 on the extinct congeners of the Notidanidaa, so far as they can be 

 determined from the evidence of detached teeth. 



Briefly reviewing the main anatomical features of the living Noti- 

 danus, in the first place, there are several peculiarities especially 

 worthy of note. The skull is remarkable from its close approach to 

 the amphistylic type of Professor Huxley. 1 Unlike all other living 

 Selachians, the upper element of the hyoid arch is extremely slender 

 and takes no part in the support of the pterygo-quadrate and man- 

 dibular cartilages ; but this is compensated for by a distinct facette 

 upon the otic process which articulates with the post-orbital process 

 of the chondrocranium. 2 The mandibular and hyoid arches thus 

 most nearly retain their primitive condition, and there is also only 

 a very slight advance upon this stage in Cestracion : 3 in this genus, 

 the pterygo-quadrate articulates with the pre-orbital region of the 

 chondrocranium, and the " hyomandibular " is only just becoming 

 worthy of that name. These characters are so important, when 

 taken in conjunction with others exhibited by the same types, that 

 in dividing the Selachii into four great suborders, Prof. Theodore 



1 T. H. Huxley, "On Ceratodus Forsteri, with Observations on the Classification 

 of Fishes," Proc. Zool. Soc. 1876, pp. 40-45. 



2 See excellent figures by C. Gegenbaur, " Das Kopfskelet der Selachier " (1872), 

 plate x. 



• 3 T. H. Huxley, he. cit. p. 42, fig. 8. 



