426 
ACTTNOPTERYGTI. 
opercular apparatus comprised nearly four-and-a-half times in the 
total length ;. maximum depth of trunk equalling about one-ninth 
of the total length of the fish. Cranium rapidly tapering to the 
acute rostrum, which is produced in advance of the mandible to equal 
one-third of the total length of the cranium ; cranial bones and 
cheek-plates ornamented with fine granulations, which are fused 
into longitudinal rugae on the rostrum and sometimes on part of 
the cranial roof; mandible and opercular bones almost smooth; 
presymphysial bone very short, scarcely longer than deep; man¬ 
dibular teeth very robust. Pelvic fins situated far behind the 
middle point of the trunk. Scales smooth, except those of the 
dorsal region, which are marked with longitudinal rugae. 
The “ single row of small close-set tubercles,” noted by Egerton 
on the ramus of the mandible, is an appearance due to the orifices 
of the sensory canal. 
Form. & Log. Purbeckian : Dorsetshire. 
28621, Head and abdominal region, lateral and partly superior 
aspect, with the base of the right pectoral fin ; Swanage. 
In the mandible the presymphysial bone is well shown, 
and the head is figured in Gunther’s ‘ Introduction to the 
Study of Pishes,’ p. 369, fig. 146 (copied in Proc. Geol. 
Soc. 1884, p. 50, fig. 4). Purchased , 1853. 
P. 6380. Imperfect cranium and the greater portion of the trunk, 
much fractured ; Swanage. The ornamentation of the 
dorsal scales is well shown, and there are slight traces of 
serrations on some of the deep flank-scales. Beckles Coll. 
Aspidorhynchus crassus, A. S. Woodward. 
[Plate XVII. fig. 11.] 
1844. Sauropsis ?nordax, L. Agassiz, Poiss. Foss. vol. ii. pt. ii. p. 122 
(name only). 
1871. Bliolidophorus minor P, J. Phillips, Geol. Oxford, p. 180, 
woodc. xl, figs. 5, 6. [Mandibular ramus ; Oxford Museum.] 
(P) 1871. JBelonostomus Jlexuous, J. Phillips, ibid. fig. 3. [Maxilla ? ; 
Oxford Museum,] 
1888. Aspidorliynchns sp., A. S. Woodward, Ann. Mag. Nat. Hist. [6] 
vol. i. p. 355. 
1890. Aspidorlvynchus crassus , A. S. Woodward, Proc. Geol. Assoc, 
vol. xi. p. 295, pi. iii. figs. 11-14. 
Type. Cranium ; British Museum. 
A small species known only by cranium and jaws. Cranium low, 
gradually tapering to the acute rostrum, which is produced in 
advance of the mandible to equal one-third of the total length of 
