CANOBIUS. 171 



Genus — Canobius, Traquair, 1881. 

 Mesopoma (pars), Traquair. 



Generic Characters. — Body fusiform ; caudal fin very heterocercal, deeply cleft, 

 inequilobate, the upper lobe elongated ; dorsal and anal fins short-based, triangular- 

 acuminate, nearly opposite each other, the former commencing oidy very slightly ill 

 front of the latter; pectorals and ventrals obscure. Suspensorium nearly vertical; 

 snout rounded, slightly projecting over the mouth; orbit large; gape moderate ; denti- 

 tion unknown. Scaies rhomboidal ; in some cases there is a median row of large imbri- 

 cating scales between the occiput and the origin of the dorsal fin. 



The type species of this genus of small fishes is Canobius Ramsay i, a form which to 

 the general configuration of a Palaeoniscid unites a disposition of the suspensorial and 

 opercular apparatus which is almost identical with the condition of these parts in the 

 Platysomid Eurynotus. Here again we have a fish which contradicts what I once con- 

 sidered to be an essential character of the Palaeoniscidae — namely the oblique direction of 

 the suspensorium — but which according to its other points of structure it would be hard 

 to exclude from that family. 



It will also be convenient to include under Canobius several other species of small 

 Palaeoniscidae which resemble the species " Ramsay i" in external form as well as in the 

 direction of the suspensorium, although in certain other points of cranial osteology, they 

 differ from that species as well as from each other. Two of these species, viz. C.pulchellus 

 and C. politus, I accordingly, in 1890, separated under the generic name of Mesopoma, 

 adding to the proposed new genus the small species from the West Lothian Oil Shales, 

 which I had previously described as Rhadinichtliys macrocephalus. However, seeing 

 the difficulty in establishing a satisfactory generic diagnosis for Mesopoma, I have come 

 to the conclusion that it is better to withdraw it for the present, and to merge its species 

 in the genus Canobius. 



Outside the boundaries of the United Kingdom a small Palaeoniscid occurs which by 

 Mr. Lawrence M. Lambe is referred to this genus. This is the Palaeoniscus (Rhadi- 

 niclithys) modulus of Sir J. W. Dawson from the Albert Shales (Lower Carboniferous) 

 of New Brunswick, which was referred also to Palaeoniscus by Newberry, but to 

 Rhadinichtliys by Smith Woodward and by Eastman. It is said to be about the same 

 length as Canobius Ramsayi, and its backwardly placed dorsal fin, with a nearly vertical 

 suspensorium, gives great probability to Mr. Lambe's idea of its generic position. 1 



1 See J.W.Dawson, ' Canad. Naturalist' (n. ser.), vol. xii, 1878, text-fig., and in 'Arcadian 

 Geology,' Suppl. p. 100, text-Eg. 1. A. S. Woodward, 'Cat. Foss. Fishes Brit. Mus.,' pt. ii, 1891, 

 p. 460. C.R.Eastman, 'Geol. Surv. Iowa,' vol. xviii, p. 292. L. A. Lambe, 'Mem. Geol. Surv. 

 Canada,' " Palaeozoic Fishes from the Albert Shales of New Bruuswick," p. 31, pi. xi, figs. 1—7. 



