140 GANOID FISIIIilS OF T[IE CARBONIFEROUS FORMATION. 



5. Rhadinichthys Macconociiii, Traquair. Plate XXIX, figs. 7 — 11. 



liiiADTNiciiTnTS MACCONOcnii, Trarjuair. Trans. Roy. Soc. Edinb., vol. xxx, 



1881, p. 30, pi. ii, figs. 12—10. 

 — — A. S. Woodward Cat. Foss. Fishes Brit. Mus., 



pt. ii, 1891, p. 464. 



Specific Characters. — Cranial roof-bones tuberculatecl ; tiie ridges on the mandible 

 so frequently interrupted as to cause the ornament to assume nearly as much of a 

 tuberculated as of a striated character ; scales not denticulated posteriorly ; dorsal fin 

 situated nearly exactly opposite the anal. 



Description. — Length from 3 to 3f inches ; shape elegantly fusiform ; the length 

 of the head contained a little more than four times in the total, and equal to the 

 depth of the body midway between the pectoral and ventral fins. 



The cranial roof-bones are ornamented with a close, comparatively coarse and 

 frequently confluent tuberculation ; the orbit is, as usual, anteriorly placed, and the 

 ethmoid forms a projection over the mouth. The suspensorium is very oblique and 

 the gape correspondingly extensive. The maxilla is of the usual form, its broad portion 

 being ornamented with closely set ridges which run parallel with its superior and 

 posterior margins; the beautifully tapering mandible is marked externally with ridges 

 which pass from behind forwards in a slightly radiating manner, but which are also so 

 frequently interrupted as to cause the ornament to assume nearly as much of a tuber- 

 culated as of a striated aspect. The operculum is of moderate size, rather broader 

 below than above; the suboperculum is rather large; both of the plates are ornamented 

 with prominent and proportionally coarse rugae, which follow mostly the lines of growth. 

 The bones of the shoulder-girdle present nothing peculiar in form and arrangement, 

 and are sculptured externally with ridges similar to those on the opercular bones. 



The scales are of medium size, rhoniboidal, as usual, diminishing in size dorsally, 

 ventrally, and posteriorly; they are low and narrow on the belly from the throat to the 

 anal fin, while those of the front part of the lateral line are proportionally higher than 

 the others. The scales of the middle line of the back are small, until just in fi'ont of 

 the dorsal fin, where a few of comparatively large size and imbricating arrangement are 

 found. In one specimen forty-five oblique dorso-ventral bands of scales may be counted 

 from the shoulder-girdle to the commencement of the lower lobe of the caudal fin. The 

 scale-ornament (PI. XXIX, figs. 8 — 11) is sharpest on the scales above the lateral line, 

 where it consists first of a few sharp grooves parallel with the anterior margin and 

 tending below to turn round along the inferior one, the rest of the area being occupied 

 by two or three slightly prominent ridges passing somewhat obliquely towards the 

 posterior margin, before reaching which they usually stop short — a marked feature in 

 this species being that on no part of the body do the scales appear to be denticulated 



