Piscrs. | DEVONIAN VERTEBRATA. 583 
CHIRACANTHUS MICROLEPIDOTUS (Ag.) 
Ref.—Ag. Old Red Fish, t. 15. f. 2. 
Desc. —Length about five inches ; head one-fifth of the length ; greatest depth (in front of the ventrals) one 
inch; dorsal Bhaut midway between the anal and ventral Se), the ‘bony ray very strong, its length equalling 
the depth of the body at its base ; other rays of the fin about half the depth of the body at its base: scales 
(seven or eight in two lines) rhomboidal ; posterior margin rounded and marked with minute, sharp, radiating 
strie crenulating the edges. 
Position and Locality—Not uncommon in the nodules of the Old Red sandstone at Lethen Bar. 
CHIRACANTHUS MINOR (Ag.) 
Ref—Ag. Poiss. Foss. Vol. II. t. 1c. fig. 5. 
Desc.—Length eight inches, depth about one inch; head short, obtuse, one-eighth of the length: scales 
minute, rhomboidal, convex, gibbous, smooth; about five or six in the space of one line; bony ray of the 
pectoral about equalling the depth of the body at its base, strong, slightly curved, longitudinally suleated ; dorsal 
and anal spines about three-fourths the depth of the body at their base ; lobes of the tail very unequal, lower 
lobe triangular, length and width of its base about equal ; upper lobe only half the width, and nearly three times 
the length of the lower. 
As M. Agassiz founded this species on a small fragment of the anterior part, the above description, from 
numerous perfect examples, may be useful. The species is almost invariably found doubled up into a loop, like 
the Acanthodes pusillus, the tip of the snout touching the middle of the back. 
« Position and Locality—Very common in the bituminous flags of the Old Red sandstone of Caithness. 
CuirAcANTHUS MuRcHISONI (Ag.) 
Ref—Ag. Poiss. Foss. Vol. II. t. 1c, f. 3 & 4. 
Dese.—Length about six and half inches; greatest depth about one and half inches ; bony rays of dorsal 
or anal fins not exceeding two-thirds the depth of the body at their base ; scales rhomboidal, about nine or ten 
in two lines, marked with very numerous minute, close, sharp, diagonal striae, edges entire. 
Position and Locality——Not uncommon in the nodules of the Old Red sandstone at Gamrie. 
CHIRACANTHUS PULVERULENTUS (M/‘Coy.) Pl. 2. B. fig. 2 
Ref —M°Coy, Ann. Nat. Hist. 2nd Series, Vol. IT. 
Desc.—Elongate, fusiform, tapering very gradually from the pectorals, where the depth is little more than 
one-sixth of the length; tail moderate, lunately forked ; the bony ray of the dorsal fin is slightly nearer the anal 
than the ventral fins, those latter being half way between the pectorals and anal; the ventral spines are about 
half the depth of the body at their base, the others are about two-thirds of the depth: scales flat, rhomboidal, 
but the length and width nearly equal, apparently not imbricated, the posterior, inferior angle tumid, pointed ; 
seven scales occupy a space of two lines ; surface dull, covered with an exceedingly minute, crowded granulation 
(only visible under a strong lens). Length eight inches. 
The squamation of this species is so peculiar that a comparison with its congeners is rendered unnecessary ; 
in general appearance it resembles the 0. Murchisoni (Ag). The head is imperfect, but seems rather pointed, 
and almost one-sixth of the entire length. 
Position and Locality —Rare in Old Red flags of Orkney. 
Explanation of Figures—P\. 2. B. fig. 2; small perfect individual, natural size; fig. 2a, scales from 
middle of somewhat larger specimen, magnified twenty-four diameters. 
[FASC. III.] 4F 
