16 
ICHTHYOTOMI. 
Chondrenchelys problematica, Traquair. 
1888. Chomlrencheh/s problemttica, U. II. Traquair, loc. cit. 
Tijpe. Iraporfeot skeleton ; Edinburgh Museum. 
Single known species. 
Form. Loc. Lower Carboniferous (Calciferous Sandstone) : 
Eskdale, Dumfriesshire. 
P. 4085. Skeleton, 0-17 m. in length, more or less perfectly 
preserved in the caudal region, and displaying the cha- 
racters of the type specimen. Purchased, 1883. 
Family CLADODONTID^. 
An indefinable family, apparently closely allied to the Pleura- 
canthidse. The only known example of the type genus, Cladodus, 
exhibits a pectoral fin in the form of a unisorial archiptorygium — 
intermediate between the truly biserial one of Pleuracanthus and 
the pectoral fin of modern Sharks '. The two halves of the pectoral 
arch are described as separate, but no other parts of the skeleton 
are yet known. 
Genus CLADODUS, Agassiz. 
[Poiss. Eoss. vol. iii. 1843, p. 190.J 
Head broad, depressed; teeth in numerous series. Crown of 
tooth consisting of a principal cone, long, subulate, pointed and 
conical, with one or more similar, but smaller, cones on either side, 
the outer of these being generally the largest. Base expanded at 
right angles to tho crown posteriorly, the front margin, bearing the 
coronal cones, being straight, the posterior semicircular. 
Cladodus mirabilis, Agassiz. 
1843. Cladodus mirabilis, L. Agassiz, Poiss. Foss. vol. iii. p. 197, 
pi. 22 b. figs. 9-13. 
1843. Cladodus miUeri, L. Agassiz, tom. cit. p. 199, pi. 22 b. figs. 22, 23. 
1855. Cladodus mirabilis, F. McCoy, Brit. Palseoz. Foss. p. 619 (in 
part). 
I860. Cladodus mirabilis, E. d’Eichwald, Lethsea Rossica, vol. i. p. 1604. 
1862. Cladodus, Morris & Roberts, Quart. Journ. Geol. Soc. vol. xviii. 
p. 105, pi. iii. fig. 6. 
1864. Cladodus mirabilis, H. Romanowsky, Bull. Soc. Imp. Nat. 
Moscou, vol. xx.xvii. no. iii. p. 166, pi. iv. fig. 31. 
' B. H. Traquair, Geol. Mag. [3] vol. v. (1888), p. 83. 
