284 
ARTURODIRA. 
arranged in definite lines. Unarmoured caudal region somewhat 
longer than the head and armoured portion of the trunk ; dorsal 
fin with about fifteen double series of endoskeletal supports, arising 
at a distance equal to its own length behind the great dorsal plate. 
Form. § Loc . Lower Old Red Sandstone : Banffshire, Rairn- 
shire, Cromarty, Ross-shire, Caithness, and Orkney 1 . 
(i.) Orkney Isles (typical C. decipiens). 
jyt, 
P. 3214-5. Two of the type specimens figured by Agassiz, op. cit. 
pi. vii. and pi. ix. fig. 2. The relative elongation of the 
haemal arches in the abdominal region is conspicuous, and 
in the second specimen the double series of supporting 
bones of the dorsal fin is distinct. The latter fossil also 
exhibits remains of a longitudinal grooved streak (calcified 
lateral line) along the vacant space originally occupied by 
the notochord; and appearances on the ventral aspect are 
suggestive of the radial cartilages of a pelvic fin attached 
to a small arched basipterygium. Enniskillen Coll. 
P. 535, P. 535 a, P. 536 a. Two of the type specimens, the first in 
counterpart and figured, op. cit. pi. viii. pi. ix. fig. 1, the 
second figured, op. cit. pi. ix. fig. 3. The anterior dorso¬ 
lateral plates in the former exhibit the rounded articular 
process on the inner margin. The apparently curved 
process of the posterior outer angle of the posterior 
ventro-lateral plate is an impression of the small curved 
pelvic basipterygium. Egerton Coll. 
P. 536. Posterior median ventral plate, figured by Agassiz, op. cit. 
pi. xxx. a. fig. 19. Egerton Coll. 
P. 3216, P. 3216 a. Two slabs from Ramna Gio, each with an im¬ 
perfect specimen and the crushed carapace of another. 
The second specimen displays the double series of about 
twelve supporting bones of the dorsal fin and a fragment 
evidently of the fin-membrane itself; also one of the 
pelvic basipterygia and a fragment of indeterminable 
fossilized tissue in the anal region. Enniskillen Coll. 
P. 550. Portion of trunk, showing dorsal fin-supports, the elon¬ 
gation of the abdominal haemal arches, and an indeter¬ 
minable patch of tissue in the anal region. Egerton Coll. 
1 This species is also considered to occur in the Russian Devonian by E. von 
Eiehwald, Leth. Rossiea, vol. i. (1860), p. 1522. 
