92 
ICHTHY0D0RTJLITE8. 
The original of the following specimen is also referable to a large 
extinct species either of Chimcera or Edaphodon :— 
P. 1160. Plaster cast of imperfect dorsal fin-spine, described and 
figured under the name of Dijoristis chimceroides, P. Ger- 
vais, Zool. et Pal. Generales (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. Eritsch (Pept. u. Eischebohm. 
Kreideform. 1878, p. 16, woodc.), from the Cretaceous of Bohemia, 
is founded upon one of the problematical teeth named Plethoclus by 
Dixon (Foss. Sussex, 1850, p. 366). The type specimen is preserved 
in the Royal 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 Chimseridm, 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 
Hcirriotta by Goode and Bean (Proc. Biol. Soc. Washington, vol. iii. 
1886, p. 104, footnote), and the type specimens are preserved in the 
Smithsonian Institution. 
?< C, 
y*- <r ~ 
(yjl - / -t 
- ^ /i&loeh'c#- 
ICHTHYODORUL1TES. 
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 
Ichth yodortjlites. 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 
