82 ACANTHODIAN SHARKS 
Further resemblances to Cladoselache are to be traced in 
the position of the fins, gill slits, eyes, mouth, nasal cap- 
sule, and in the structures of the caudal fin (Kner), and of 
the lateral line. The teeth, however, are no longer of the 
derm-denticle pattern; they have become few in number, 
_large, and “degenerate” in their fibrous structure (Fig. 
88, A). The fins are clearly more per- 
fect balancing organs than those of 
the older shark ; their anterior rim is 
Fig. 88 A.—Teeth of formed by a stout spine, representing, 
Acanthodopsis wardi. Xt the present writer believes, the con- 
From_sketeh-after~speci- Rates | 
men in-British Museum. | Crescence of the radial fin supports ; 
it is heavily crusted over with the 
calcifications of shagreen denticles. The functional fin 
area has thus become dermal, and is lacking in supports, 
excepting in the pectoral fin. This, as the most highly 
specialized of all the body fins (p. 41), appears in some 
cases to have evolved ‘strengthening (dermal) rays in its 
proximal portion (as in Figs. 87 and 32). 
. 
Fig. 89. — Climatius scutiger, Egert. X1. (From ZITTEL, after. POWRIE.) 
Old Red Sandstone, Forfarshire. 
In connection with these fin structures the remarkable 
Acanthodian, Climatius (Fig. 89), should finally be men- 
tioned. In this form the paired fins are represented by a 
series of fin spines whose size grades backward from the 
pectoral region; a series of paired fins appear, therefore, 
