SEMTONOTIDiE. 
51 
Trunk irregularly cycloidal, with, 
strongly-arched hack; marginal 
teeth slender and styliform ; dor¬ 
sal and anal fins opposed, not 
much extended : all scales rhom¬ 
bic, with thick inner rib, very 
deep and narrow on flank ; ridge - 
scales conspicuous . Cleithrolepis (p. 154). 
Trunk irregularly cycloidal, with 
strongly-arched back; dorsal fin 
much extended and anal opposed 
to its hinder portion; abdominal 
scales rhombic, with thick inner 
rib; caudal scales more or less 
cycloidal. Aetheolepis (p. 157). 
Trunk irregularly cycloidal, with ab¬ 
dominal protuberance; marginal 
teeth slender and styliform: dorsal 
fin much extended and anal op¬ 
posed to its hinder half; all scales 
rhombic, with thick inner rib, but 
those of caudal region compara¬ 
tively delicate ; ventral ridge- 
scales conspicuous . Tetragonolepis (p. 158). 
Genus AGRMTROPHORUS, Traquair. 
[Quart. Journ. Geol. Soc. vol. xxxiii. 1877, p. 565.] 
Trunk fusiform. Teeth slender; opercular apparatus well- 
developed, with a narrow arched preoperculum. Pins small, with 
very large fulcra; dorsal fin short, opposed to the space between the 
pelvic pair and the anal; caudal fin symmetrical, slightly forked; 
Scales rhombic, smooth or feebly ornamented, the dorsal ridge- 
series inconspicuous ; the scales of the flank not much deeper than 
broad, and those of the ventral aspect nearly equilateral. 
All the fishes placed here were originally assigned to the genus 
Palceoniscus, and their distinctness was first pointed out by C. P. 
Liitken, Palseontogr. vol. xxii. (1873), p. 26, footnote. 
Acentrophorus varians (Kirkby). 
1862. Paiceoniscus varians , J. W. Kirkby, Ann. Mag. Nat. Hist [3] 
vol. ix. p. 267. 
1864. Palceoniscus varians , J. W. Kirkby, Quart. Journ. Geol. Soc. 
vol. xx. p. 353, pi. xviii. fig. 2. 
1877. Acentrophorus varians, It. H. Traquair, Quart. Joum. Geol. Soc. 
vol. xxxiii. p. 565. . 
E 2 
