N0TACANTHIDJ2. 
169 
Notacanthus and two or three closely allied genera still exist in 
the deep sea. An account of the osteology and anatomy of some of 
the soft parts of the type genus is given by Giinther 1 , and there is 
some reason to believe that the fish is truly physostomous 2 . 
Vaillant has observed bone-lacunse in soveral parts of the skeleton 3 . 
Genus PRONOTACANTHUS, novum. 
An imperfectly known genus, with laterally-compressed trunk 
and an excessively elongated abdominal region which comprises at 
least 70 vertebrae. Teeth recurved, in single regular series in the 
mandible. A regular, spaced series of dorsal fin-supports extending 
along the whole length of the abdominal region, each support 
e xpanded distally, but not bearing either fin-ray or spine. 
Pronotacanthus differs from all the existing genera in the absence 
°f dorsal spines or fin-rays. It has already been mentioned in 
Ann. Mag. Nat. Hist. [7] vol. v. (1900), p. 322. 
Pronotacanthus sahel-almae (Davis). 
[Plate XV. figs. 1, 2.] 
1887. Anguilla sahd-cimce, J. W, Davis, Trans. Roy. Dublin Soc. [2] 
vol. iii. p, 625, pi. xx. fig. 2. 
Pype. Imperfect fish ; British Museum. 
The type species, attaining a length of about 0 - 25. Length of 
head with opercular apparatus twice as great as the maximum 
depth of the trunk, which is contained about eight times in the 
distance between the paired fins. Number of dorsal fin-supports in 
the same space about 52. 
Form. Sf Loc. Upper Cretaceous; Sahel Alma, Mt. Lebanon. 
46535, P. 4741. Typo specimen in counterpart, unsatisfactorily 
described by Davis loc. cit., with figure restored from both 
sides of the fossil. The right side of the fossil is re-drawn 
in PI. XV. fig. 1. The head is distorted and too imperfect 
for description, but the bones bordering the mouth are 
shown to be comparatively stout, and there seems to be 
an antorbital cheek-plate traversed by a branching sensory 
canal. The much-constricted vertebral centra are mostly 
broken along the middle and partly obscured by the 
1 A. Giinther, Deep Sea Fishes, 1 Challenger’ Rep. — Zool. vol. xxii. (1887), 
P 245, pi. lx. fig 8 . 9_i5 
U. Vaillant, Exptid. Scient. Travailleur et Talisman. — Poissons (1888), 
P- 333. 
3 L. Vaillant, op. cit. p. 323. 
