ISO GANOID FISHES OF THE CARBONIFEROUS FORMATION. 



Geological Position and Locality. — Near Glencartholm, Eskdale, in the fish-bearing 

 shales of Calciferous Sandstone (Lower Carboniferous) age. The original specimens 

 were collected by the Geological Survey of Scotland. 



5. Canobius macrocephalus, Traquair, sp. Plate XL, figs. 1 — i. 



Khadinichthys macrocephalus, Traquair. Proc. Roy. Soc. Edinb., vol. xvii, 



1890, p. 398. 

 Mesopoma macrocephalujj, Traquair. Ann. Mag. Nat. Hist. [6], 1890, vol. 



vi, p. 493. 

 Canobius macrocephalus, A. 8. Woodward. Cat. Fobs. Fishes Brit. Mus., pt. ii, 



p. 433. 



Specific Characters. — Attaining a length of 4 inches; length of head, which is 

 proportionally short and deep, contained a little over four times in the total ; depth 

 of body at shoulder equal to twice that of tail-pedicle, so that the form of the fish 

 tapers conspicuously from before backwards; scales mostly smooth, with very minute 

 denticulations ; no specially large scale in the middle line of the back; cranial roof- 

 bones tuberculo-striate ; suspensorium nearly vertical in direction. 



Description. — Owing to the frequent distortions to which these fishes have been 

 subjected in the process of fossilisation, it is difficult to lay down their proportions with 

 perfect accuracy ; however, we may specially note the large size of the head and the 

 tapering form of the body from the shoulder to the tail-pedicle. 



The cranial roof-bones have a tuberculo-striated ornament ; the orbit is large; the 

 suspensorium nearly vertical. No good view is to be had of the facial bones in spite 

 of the large number of specimens which have been collected ; nevertheless the form 

 of the maxilla and the presence of branchiostegal rays or plates may be noted in some 

 examples. 



The dorsal fin commences at or about twice the length of the head from the tip 

 of the snout, and is of the usual acuminate shape ; as is also the anal, the commence- 

 ment of which is only a very small distance behind it. The rays of both fins are rather 

 distantly articulated, the joints being either perfectly smooth or having at most a single 

 fine longitudinal furrow. The caudal is small, but completely heterocercal, and deeply 

 cleft ; its rays are like those of the dorsal and anal. 



The pectoral is seen in one specimen ; it is small, with very few rays, the careful 

 examination of which leads to the conclusion that, as in Rhadinichthys, the principal 

 rays were unarticulated till towards their distal extremities. Traces of the ventral are 

 seen just in the middle between the pectoral and the anal. 



The scales are of moderate size, largest on the flank, and becoming smaller on the 

 belly, the caudal extremity, and the back, although there is no median row of enlarged 



