238 IOWA GEOLOGICAL SURVEY 



Family HOLOPTYCHUDAE. 



Body fusiform, with cycloidal, deeply overlapping scales, more 

 or less enamelled. Head and opercular apparatus with well de- 

 veloped membrane hones ; parietals large and separate ; f rontals 

 separate, not fused into a continuous plate with adjoining ele- 

 ments; no parietal or frontal foramen; interopereulum absent; 

 jugular plates comprising one large pair, flanked on either side 

 by a lateral series. Dentary bone of mandible thin and deep, 

 bearing a series of small teeth, and with well developed infra- 

 dentaries, much bent inwards below; an inner series of few, 

 large, broad shuttle-shaped bones, 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 complex infoldings, 

 appearing closely intertwined when viewed in transverse sec- 

 tion, these producing superficial vertical flutings. Pectoral fins 

 acutely lobate, pelvic fins either acutely or obtusely lobate ; two 

 remote dorsal fins; anal fin single; caudal fin diphycercal or 

 heterocercal. (Woodward.) 



The foregoing family definition, which we have extracted 

 from Smith Woodward, is based chiefly upon the structural 

 characteristics of the typical genus Holoptychius, well preserved 

 specimens of which occur plentifully in the Scottish Old Eed 

 Sandstone, and have been obtained also from Belgium and 

 Russia. With the exception of the closely related Glyptolepis 

 quebecensis Whiteaves,* by some writers included with Holop- 

 tychius, no member of this family is represented in the North 

 American Devonian by completely preserved remains, and by 

 far the greater number of species is founded upon detached 

 scales. The teeth described by Leidy under the name of Ape- 

 dodus priscns,-\ from the Catskill of northern Pennsylvania, do 

 not appear to differ from those of Holoptychius by any recog- 

 nizable characters. On the other hand the accompanying Saurip- 



* Whiteaves, J. F., Trans. Roy. Soc. Canada, 1889, vol. 6, 4, p. 77, pi. 5, fig. 4. 



t Leidy, J., Journ. Acad. Nat. Sci. Philad. 1856, ser. 2, vol. 3, p. 164, pi. 17, 

 figs. 5, 6. 



