582 BRITISH PALAOZOIC FOSSILS. [ Pisces. 
Genus. CHIRACANTHUS* (4g.) 
Gen. Char.—Body of moderately small size, ovate ; one dorsal fin placed considerably in front of the anal, 
opposite the space between anal and ventral fins ; anal fin rather smaller than the dorsal; ventral fin equalling 
the anal one in size, a little in front of the middle of the body ; pectorals moderate, pointed ; all the fins with a 
strong bony ray in front ; upper lobe of the tail much longer and more pointed than the lower. 
CHIRACANTHUS GRANDISPINUS (M* Coy). Pl. 2. B. fig. 1. 
* Ref.—M°Coy, Ann. Nat. Hist. 2nd Series, Vol. IT. 
Desc.—Elongate, fusiform ; tail slender; caudal fin large, moderately lobed; bony spines of the anal, 
ventral and pectoral fins of great size, their length being about three-fourths of the depth of the body at their 
hase; the spine of the anal fin is gently curved backwards, those of the ventrals and pectorals straight ; dorsal 
spine also of great thickness, but its length unknown, situated a little behind the line of the ventrals; scales 
rhomboidal, length and width nearly equal, about seven in the space of two lines, convex, strongly striated 
diagonally in the direction of the length of the fish, one of the diagonal grooves generally much deeper than 
the rest in the middle. Length from the base of pectoral fin to extremity of tail nearly eight inches, depth 
of body at base of dorsal fin two inches; pectoral and ventral spines nearly one and three-fourths of an inch 
long, and one and half line wide at base, all apparently smooth. 
In the great size and strength of its spines this resembles a great Diplacanthus rather than a species of 
the comparatively feebly armed genus Chiracanthus ; it has however no second dorsal opposite the anal fin, and 
is clearly a peculiar species of the latter genus; from all the species of which the very large spines and strongly 
striated scales distinguish it. 
The brancbiostegous rays are very numerous, slender, and distinctly ossified. The cincture supporting 
the pectorals is very strong and bony. 
Position and Locality—Rare in the bituminous flags of the Old Red at Orkney. 
Erplanation of Figures —P1. 2. B. fig. 1, natural size; at the point of greatest curvature of the back the 
single-dorsal fin and its thick spine are partially preserved; fig. ] a, scale from near the tail, magnified twenty- 
four diameters, 
CHIRACANTHUS LATERALIS (J/*Coy). 
Ref —MCoy, Ann. Nat. Hist. 2nd Series, Vol. IT. 
Dese.—Slender, fusiform ; dorsal nearly intermediate between the anal and ventral fins, slightly nearer the 
latter; spines of the ventral and anal fins yery small, slightly curved, not more than half the depth of the body 
at their base, the dorsal spine about one-fifth longer than the others; sides of the body impressed by a 
strong, straight, lateral line, rather nearer the ventral than the dorsal margin ; scales rhomboidal, a little higher 
than wide, smooth, each with a vertically diagonal, strong, angular, mesial gibbosity, about six scales in the 
space of one line; length of anal spine seven lines; depth of body at base of dorsal fin one and a quarter 
inch. 
I have only seen two tolerably good specimens of this species, which in size and general form, both of body 
and spines, resembles closely the C. pulverulentus (M*Coy), from which it is distinguished by its smaller and 
more pointed, vertically gibbous, smooth scales, and having slightly smaller spines; and the ventral and anal 
spines being proportionally further apart, being about equal to the depth of the body at the ventrals in the 
former, but exceeding it in the present species. What renders the C. lateralis most remarkably distinct from 
the other species of this and the allied genera, is the presence of a very strongly marked lateral line. 
Position and Locality—Rather rare in the Old Red sandstone flags of Orkney. 
* Spelt Cheiracanthus, by Agassiz. 
