372 
ACTIKOPTEErGII. 
in parts by transverse fractures. An im pression of part 
of the frontal "region bears traces of minute tubercles 
arranged, along the radiating lines of growth. The oper¬ 
culum is quite smooth. The vertebral centra are delicate 
much-constricted cylinders, apparently pierced by a 
persistent thread of notochord; and large transverse 
processes bearing the ribs are conspicuous in the anterior 
portion of the abdominal region. Long, very slender 
intermuscular bones are also seen. The neural and 
haemal spines in the caudal region are very short, broad, 
and recumbent. The pelvic fin-suppor/:s are expanded 
laminae, and the anterior pelvic fin-spine is nearly as long 
and stout as the foremost divided ray, which seems to be 
followed by five others. Of the dorsal fin, only a fragment 
is distinguishable opposite to the anal. Tne diminutive 
anal fin-spine is borne by a considerably expanded 
support; while the length of the foremost divided anal 
ray probably exceeds the depth of the trunk at its inser¬ 
tion. The imperfect caudal fin, consisting of very broad 
rays, seems to have been forked. A series of enlarged 
dermal scutes is only preserved between the pelvic and 
dorsal fins on one side; but the whole of the trunk is 
covered by very small, rounded or rhomboidal scutes of 
uniform size, which do not appear to have been in 
contact. Parchased, 1862. 
Genus AULORHYNCHUS, Gill. 
[Proc. Acad. Kat. Sci. Philad. 1861, p. 169.] 
Syn. Aidiscops, W. Peters, Monatsb. k. preuss. Akad. 1866, p. 610. 
Protosyngnathus, W. von der Marck, Palaoontogr. vol. xxii. 1876, 
p. 406. 
Premaxilhe much expanded, and mandible prominent; marginal 
teeth acute, almost in one series ; palate tooth.less. Vertebrae about 
50 or 60 in total number, rather more than half being in the caudal 
region. Pelvic fins far forwards, with one spine and four divided 
rays, their supports in contact with the pectoral arch. About 25 
separate spines, diminutive and equal in size, in front of dorsal fin ; 
soft dorsal and anal nearly equal and opposite, acuminate in front; 
caudal fin small, slightly forked. No scales, but small bony scutes 
buried in skin in few longitudinal series. 
Only one existing species of this genus is known from the North 
Pacific Ocean. 
