﻿92 lOnTHYODORULITES. 



The original of the following specimen is also referable to a large 

 extinct Bpecies either of Chimcera or Edaphodon : — 



P. 1160. Plaster cast of imperfect dorsal fin-spine, described and 

 figured under the name of Dipristis chimceroides, P. Ger- 

 vais, Zool. et Pal. Generates (1867-69), p. 241, pi. xlvi. 

 fig. 5 ; Miocene, Leognan, Gironde. Egerton Coll. 



Either to Chimcera or Edaphodon may be assigned the fragments 

 of teeth from the Molasse of Baltringen, Wiirtemberg, named 

 Chimcera deleta, J. Probst, Wiirtt. Jahresh. vol. xxxviii. (1882) 

 p. 131, pi. ii. fig. 17. 



The so-called Chimcera furcata, A. Fritsch (Kept, u. Fische bbhm. 

 Kreideform. 1878, p. 16, woodc), from the Cretaceous of Bohemia, 

 is founded upon one of the problematical teeth named Plethodus by 

 Dixon (Foss. Sussex, 1850, p. 366). The type specimen is preserved 

 in the Koyal Bohemian Museum, Prague, and has been examined 

 by the present writer. 



It is interesting to add that a small Chimseroid fish, exhibiting the 

 typical dentition of the Chimseridae, but destitute of a rostral spine 

 both in the male and female, has lately been discovered in the deep 

 sea off the Atlantic coast of North America. The genus is named 

 Harriotta by Goode and Bean (Proc. Biol. Soe. Washington, vol. iii. 

 1886, p. 104, footnote), and the type specimens are preserved in the 

 Smithsonian Institution. 



ICHTHYODORULITES. 



The characters of the dermal spines and tubercles of cartilaginous 

 fishes vary so much in the different genera, and are sometimes so 

 completely identical when other parts are quite distinct, that all 

 fossils of this nature hitherto only discovered in an isolated condition 

 may be conveniently grouped together under the denomination of 

 Ichthyodoeulites. The term was first employed by Buckland and 

 De la Beche, who were the earliest to discover the true nature of 

 these fossils ; it was subsequently applied by Agassiz (op. cit.) to all 

 fossil spines of Elasmobranch and Chimaeroid fishes, whether corre- 

 lated with the teeth or not ; and we now propose to restrict the 

 name to those detached dermal spines, tubercles, and plates which 

 exhibit the microscopical structure of vascular dentine, and are thus 



