536 
ACTINOPXERYGTI. 
head continuing the downward slope of the back in front of the 
peak, with a slight convexity above and in advance of the orbit, 
below which the facial profile is more abrupt; margins of maxilla, 
premaxilla, and dentary toothless ; inner surface of maxilla and 
pterygoid with cluster of small tubercular teeth; oral aspect of 
pterygoid and splenial bones with two sharp longitudinal ridges, 
meeting posteriorly, and more or less coarsely denticulated. Fin- 
rays closely articulated and distally bifurcating; fulcra present on 
all the fins. Pectoral fins small and delicate, laterally placed; 
[pelvic fins unknown]. Dorsal and anal fins of nearly equal size 
and shape, arising behind the dorsal and ventral peaks and termi¬ 
nating at the base of the caudal pedicle, high and acuminate in 
front, low and fringe-like in the posterior two-thirds; caudal fin 
deeply cleft, nearly equilobate. Scales ornamented with tubercu- 
lations and striae, with smooth hinder border, and narrow over¬ 
lapped anterior border ; principal flank-scales very deep and narrow, 
with large anterior inner keel, and a large, broad, peg-and-socket 
articulation extending nearly the entire width of the scale; scales 
dorsally and ventrally and towards the caudal pedicle less deep in 
proportion to their breadth; scales of upper caudal lobe relatively 
small and lozenge-shaped. Well-developed ridge-scales present 
only upon the upper caudal lobe. 
The type species of this genus is known only by a detached 
splenial bone, which is insufficient for precise diagnosis. It is de¬ 
scribed as follows :— 
Cheirodus pes-rance , F. M‘Coy, Ann. Mag. Hat. Hist. [2] vol. ii. 
(1848), p. 131, and Brit. Pabeoz. Foss. (1855), p. 616, 
pi. iii. o. fig. 9; B. H. Traquair, Ann. Mag. Hat. Hist. [5] 
vol. ii. (1878), p. 17 ; J. W. Davis, Trans. Boy. Dublin Soc. 
[2] vol. i. (1883), p. 523, pi. lxiii. fig. 5.—Upper Carboni¬ 
ferous Limestone ; Derbyshire. [Woodwardian Museum, 
Cambridge.] 
Cheirodus granulosus (Young). 
1866. Amphicentrum granulosum , J. A r oung, Quart. Journ. Geol. Soc. 
vol. xxii. p. 306, pi. xx. 
1875. Amphicentrum granulosum , B. H. Traquair, Ann. Mag. Hat. 
Hist. [4] vol. xvi. p. 273, pi. ix. 
1875. Amphicentrum granulosum , J. Ward, [Proc.] H. Staffs. Hat. 
Field Club, p. 236. 
1878. Cheirodus granulosus, B, H. Traquair, Ann. Mag. Hat. Hist. [5] 
vol. ii. p. 17. 
