GYMNODONTIDJS. 
571 
spines with two horizontally-ex- 
tended roots Diodon (p. 571). 
II. Caudal region aborted. 
Both jaws fused at symphysis, and no 
dental plates . . Orthagoriscus (p. 676). 
Genus TETRODON, Linnaeus. 
[Syst. Nat. od. 10, 1758, p. 332 (7'etraodon).] 
Each jaw with median suture at symphysis, the sharp edge 
strengthened with dental plates. Separate caudal fin. Dermal 
spines small or absent, always without expanded root. 
The following specimens seem to be jaws of undetermined species 
of this genus : — 
P. 6130. Imperfect ramus of jaw ; Miocene, Mt. San Giuseppe, 
Cagliari, Sardinia. 
Presented ly Prof. D. Lovisato, 1889. 
47033. Two rami; Lower Pliocene, Orciano, Tuscany. 
Purchased, 1875. 
P. 5524. Plaster casts of two rami; Pliocene, N. Italy. 
Presented hy Prof. O. Capellini, 1888. 
Extinct species, not represented in the Collection, have also been 
described as follows : — 
Tetrodon lawleyi, A. Carraroli, Rivista Ital. Paleont. vol. iii. 
(1897), fasc. 3, p. 26, pi. i. figs. 6, 7.— Pliocene; Piacentin. 
[Jaws.] 
Tetrodon pygmeeus, A. de Zigno, Mem. 11. Istit. V eneto, vol. xxiii. 
(1887), p. 27, fig. 8. — Upper Eocene; Monte Bolca. 
[Very small fish; Zigno Coll., University of Padua.] 
Tetrodon scillce, R. Lawley, Nuovi Studi Pesci, etc. Collino 
Toscane (1876), p. 80, pi. iii. fig. 3 (wrongly identified 
with Diodon scillce, Ag.). — Pliocene ; Tuscany. [Jaws.] 
Genus DIODON, Linnaeus. 
[Syst. Nat. ed. 10, 1758, p. 334.] 
Syn. Megalurites, O. G. Costa, Atti Accad. Pontan. vol. v. 1850, p. 370. 
Enneodon, J. J. Heckel (i non Prangner, 1845), Sitzungsb. k. Akad. 
Wiss., math.-naturw. Cl. vol. xi. 1854, p. 127. 
Heptadiodon, H. G. Bronn, Leth. Geogn. ed. 3, vol. iii. 1855, 
p. 677. 
