322 
CROSSOPTEKYGII. 
each supporting a ‘ laniary ’ tooth; a pair of: similar teeth on the 
roof of the mouth, but the marginal upper dentition feeble. Teeth 
conical, with a very small pulp-cavity, of which the walls exhibit 
Pig. 48. 
Transverse section of Holoptychian (Dendrodont) Tooth, much magnified; 
after Pander. 
complex infoldings, appearing closely intertwined when viewed in 
transverse section, these producing superficial vertical flutings. 
Pectoral fins acutely lobate, pelvic fins acutely or obtusely lobate; 
two remote dorsal fins; anal fin single ; caudal fin diphycercal or 
heterocercal. 
The typical Holoptychius is the single genus of this family as yet 
definitely determined. 
Genus HOLOPTYCHIUS, Agassiz. 
[Agassiz in Murchison’s Silur. Syst. 1839, p. 599 ( Holoptychus ), 
and Poiss. Poss. V. G. R. 1844, p. 68.] 
Syn. Dendrodus, R. Owen, Microscopic Journal, vol. i. 1841, p. 4. 
Platyynathus, L. Agassiz, Poiss. Foss. V. G. R. 1844, pp. 61, 76. 
Lcminodus, L. Agassiz, ibid. 1845, p. 83. 
(?) Sclerolepis , E. von Eichwald, Bull. Soc. Imp. Nat. Moscou, 
vol. xvii. 1844, p. 828. 
(?) Apedodus, J. Leidy, Journ. Acad. Nat. Sci. Philad. [2] vol. iii. 
1856, p. 164. 
(As subgenus) Glyptolepis, L. Agassiz, Poiss. Foss. Y. G. R. 1844, 
p. 62 (in part). 
Body short and stout, not much laterally compressed ; scales large 
and rounded, the exposed surface marked with large, longitudina 
