﻿284 ARTHRODIRA. 



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. <$f Loc. Lower Old lied Sandstone : Banffshire, Nairn- 

 shire, Cromarty, Ross-shire, Caithness, and Orkney 1 . 



(i.) Orkney Isles (typical C. decipiens). 



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. Ennislcillen 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 

 r 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 Eamna 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. Ton 

 Eichwald, Leth. Rossica, vol. i. (1860), p. 1522. 



