34 
ACTHfOPTERYGII. 
P. 7398. Plaster cast of tail, the original being the type specimen 
described by Egerton, loc. cit .; Lyme Regis. This is 
supposed to belong to the same individual as one of the 
following specimens. 
28714. Crushed remains of head and pectoral arch, with a few 
fragmentary neural arches of the trunk and some well- 
preserved pectoral fin-rays, noticed by Egerton, loc. cit., 
and by the present writer in Proc. GeoL Assoc, vol. xi. 
(1889), p. 36 ; Lyme Regis. The tuberculations on the 
pectoral fin-rays are shown. Purchased , 1853. 
28714 a. Slab exhibiting the external tuberculated surface of three 
of the cranial roof-bones and other fragments, with an 
imperfect clavicle, described by Egerton, loc. cit .; Lyme 
Regis. The two principal cranial bones are described as 
mastoids (i. e., squamosals), and the clavicle appears to be 
referred to as “ suprascapula.” Purchased , 1853. 
Genus GYROSTEUS, A. S. Woodward. 
[Proc. Geol. Assoc, vol. xi. 1889, p. 36 (ex Agassiz, MS.).] 
An imperfectly definable genus comprising fishes of large size, 
hitherto known only by fragmentary specimens. External bones 
with or without a feeble ornamentation, destitute of ganoine; jaws 
toothless ; maxilla arched, not much expanded behind, but with a 
great upward and inward extension in its anterior half for palatine- 
pterygoid articulation; hyomandibular completely ossified; sub¬ 
operculum (?) large and quadrate. Small ossified ribs present (?).' 
Scales absent, except on the upper caudal lobe, where they are 
thick; caudal fulcral scales large, without ganoine. 
Gyrosteus mirabilis, Agassiz, MS. 
1844. Gyrosteus mirabilis, L. Agassiz, Poiss. Foss. vol. ii. pt. ii. p. 179 
(name only). 
1855. Sepia incomposita, M. Simpson, Foss. Yorkshire Lias, p. 21. 
[Fragment of bone ; Whitby Museum.] 
1858. Gyrosteus mirabilis , Sir P. Egerton, Phil. Trans, p. 883. 
1876. Gyrosteus mirabilis, J. F. Blake, in Tate & Blake, Yorkshire 
Lias, p. 256, pi. ii. figs. 2, 3. 
1889-90. Gyrosteus mirabilis, A. S. Woodward, Proc. Geol. Assoc, 
vol. xi. p. 32, figs. 2-7; and The Naturalist, 1890, p. 101, 
figs. 1-6. 
