568 
ACT IN OPTERYGII. 
vi. no. 4 (1885), p. 5, figs. 3-5. — Upper Eocene ; Monte 
Bolca. [Imperfect fish ; Geological Museum, University 
of Padua.] 
Genus ACANTHODERMA, Agassiz. 
[Poiss. Foss. vol. ii. pt. ii. 1844, p. 251.] 
A supposed extinct genus, not yet clearly distinguished from the 
existing Balistes. [Teeth unknown.] Pectoral fins very small ; large 
pelvic hone without fins or spine ; one large dorsal spine, followed 
by about two very small and comparatively slender spines ; posterior 
dorsal and anal fins low and much extended ; caudal fin rounded. 
Dorsal tubercles small and shagreen-like, apparently none en- 
larged. 
The name Acanthoderma was preoccupied by Cantraine in 1835, 
but may be retained until the extinct species placed here is satis- 
factorily known. 
Acanthoderma spinosum, Agassiz. 
1842-44. Acanthoderma spinosu?n, L. Agassiz, Poiss. Foss. vol. ii- pt. 11 ■ 
p. 252, pi. lxxv. fig. 4. 
1842-44. Acanthoderma ovale, L. Agassiz, tom. cit. pt. ii. p. 251 , 
pi. lxxv. fig. 3. [Distorted fish ; Neuchatel Museum.] 
1879. Acanthoderma orbiculatum , O. Ileer, Urwelt d. Schweiz, ed. -, 
p. 257, with fig. [Distorted fish ; Glams Museum.] 
1886. Acanthoderma spinosum, A. Wettstein, Fischfauna Tertiaer. 
Glamersehief. (Denkschr. schweiz. Palaeont. Ges. vol. xiii.), P- 
Type. Imperfect fish ; British Museum. 
The type species, attaining a length of about 0 - 12. Maximum 
depth of trunk equalling length of vertebral column, which seems 
to comprise 1 7 vertebra;. Large dorsal spine with a row of large 
tubercles along its anterior border, partly ribbed, partly tuberculated 
on its aides. Posterior dorsal fin occupying half of back, with 20 
to 25 rays : anal fin shorter and apparently with fewer rays. 
Form, df Loc. Oligocone : Canton Glarus, Switzerland. 
P. 500, P. 3973. Imperfect type specimen, in counterpart, de- 
scribed and figured by Agassiz, loc. cit.; Engi. There are 
indications of one or perhaps two very small spines 
behind the large dorsal spine. 
Eyerton § Enniskillen Colls. 
1819. Scattered but well-preserved remains of fish; Engi. A 
