﻿24 ACANIHODII. 



mesial suture. Both these elements have precisely the appearance 

 of membrane-hones ; and in some genera (e. g. Parexus, No. P. 130, 

 p. 35) the conformation of the scales in the pectoral region so inti- 

 mately depends upon their form and position, that they are evidently 

 of a superficial character. We therefore venture to determine them 

 as clavicles and infraclavicles. The truncated extremity of the 

 pectoral fin-spine (s.) directly abuts against the angle of the 

 supposed clavicle, while that of the mesial spine (m.) is chiefly 

 apposed to the same element, though in part also to the infraclavicle. 

 The axes of these two spines are inclined towards one another, and 

 at their proximal extremity they are firmly united by a triangular 

 mass of hard tissue (6), which is probably to be regarded as the 

 basipterygium or basal cartilage. 



Diplacanthus striatus, Agassiz. 



1841. " Ichthyolite," H. Miller, Old Red Sandstone, pi. viii. fig. 2. 



1842. Diplocanthus crassisimus, P. Duff, Geol. Moray, p. 71, pi. x. fig. 2. 

 1844. Diplacanthus striatus, L. Agassiz, Poiss. Foss. V. G. R. pp. 34, 



41, pi. xiv. figs. 1-5. 

 1844. Diplacanthus striatulus, L. Agassiz, ibid. pp. 34, 42, pi. xiii. figs. 



3, 4. [Forres Museum and British Museum.] 

 1844. Diplacanthus crassispinus, L. Agassiz, ibid. pp. 34, 43, pi. xiii. 



figs. 1, 2, pi. xiv. figs. 6, 7. [British Museum, in part.] 

 1848. Diplacanthus gibbus, F. M'Coy, Ann. Mag. Nat. Hist. [2] vol. ii. 



p. 301. [Woodwardiau Museum, Cambridge.] 

 1855. Diplacanthus gibbus, F. M'Coy, Brit. Palaeoz. Foss. p. 584, pi. ii b. 



fig. 4. 

 1888. Diplacanthus striatus, R. H. Traquair, Geol. Mag. [3] vol. v. 



p. 512. 



Type. Nearly complete fishes ; Edinburgh Museum (in part). 



The type species, usually attaining a length of # 07-0-l. Body 

 robust, but elongated, the greatest depth being contained about 

 four and a half times in the total length. Fin-spines very stout, 

 coarsely striated longitudinally. Pectoral fin-spines much arched 

 and sharply pointed, the median spines relatively large ; pelvic fin- 

 spines scarcely half as large as the pectoral. First dorsal spine 

 much stouter and larger than the second, placed almost immediately 

 above the pectoral arch; second dorsal spine opposed to the anal 

 and somewhat larger than the latter. Scales smooth. 



Form, fy Log. Lower Old Red Sandstone : Cromarty, Banffshire, 

 Nairnshire, Ross-shire, and Orkney Isles. 



19073-74. Imperfect specimen, in counterpart ; Cromarty. 



Purchased, 1S45. 



