PYCNODONTIDiE. 
233 
Genus GYRODUS, Agassiz. 
[Poiss. Foss. vol. ii. pt. i. 1833, p. 16, and pt. ii. 1844, p. 223.] 
Syn. Stromateus, H. D. de Blainville, Nouv. Diet. d’Hist. Nat. vol. xxvii. 
1818, p. 333. 
Trunk deeply fusiform or discoidal, with a slender abbreviated 
caudal pedicle. Head and opercular bones ornamented with 
tubercles; cheek and gular region covered with small, imbricating, 
cycloidal scales; teeth more or less rugose and mammillated, those of 
the vomer in five, and those of the splenial in four regular series. 
Neural and haemal arches of axial skeleton of trunk not expanding 
sufficiently to encircle the notochord. Fin-rays robust, closely 
arranged, articulated and divided distally. Pelvic fins present; 
dorsal and anal fins low and fringe-like, except in front where they 
rise to an elevated point, these two fins arising at about the same 
point and not extending in advance of the hinder half of the trunk ; 
caudal fin deeply forked, with slender lobes. Scales tuberculated 
or rugose, covering the whole of the trunk. 
Gyrodus macrophthalmus, Agassiz. 
1833. Microdon abdominalis, L. Agassiz, Poiss. Foss. vol. ii. pt. i. p. 16. 
1839-44. Gyrodus macrophthalmus , L. Agassiz, ibid. vol. ii. pt. ii. 
pp. 224, 301, pi. Ixvii. 
1839-44. Gyrodus rugosus, L. Agassiz (ex Minister MS.), ibid. p. 227, 
pi. lxix. [Nearly complete fish ; Palaeontological Museum, 
Munich.] 
1842. Gyrodus mceandrinus, G. von Munster, Neues Jahrb. p. 45. 
[Ditto.] 
1851. Gyrodus macrophthalmus , A. Wagner, Abh. k. bay. Akad. Wiss., 
math.-phys. Cl. vol. vi. p. 28. 
1851. Gyrodus rugosus, A. Wagner, ibid. pp. 29, 45, 56. 
1851. Gyrodus mceandrinus, A. Wagner, ibid. p. 30. 
1862. Gyrodus macrophthalmus , A. Wagner, ibid. vol. ix. p. 336 (in 
part). 
1862. Gyrodus rugosus , A. Wagner, ibid. vol. ix. p. 337. 
1862. Gyrodus dichactinius, T. C. Winkler, Descript. Poiss. Foss. 
Solenhofen (Natuurk. Verhandl. Holland. Maatsch. [2] vol. xiv.), 
p. 67, fig. 12. [Nearly complete fish ; Teyler Museum, Haarlem.] 
1881. Gyrodus macrophthalmus, B. Vetter, Mittheil. k. mineral.-geol. 
. JVlus. Dresden, pt. iv. p. 20 (in part), 
1887. Gyrodus macrophthalmus, K. A. von Zittel, Handb. Paheont. 
vol. iii. p. 239, fig. 251. 
Type. Nearly complete fish ; Paleontological Museum, Munich. 
The type species, attaining a length of about 0*3. Maximum 
