278 
ACIINOPTERYGIl. 
denticles on the scales is seen immediately behind the 
anal fin. Noticed in Proc. Zool. Soc. 1896, p. 504. 
History unknoiun. 
Notogoneus longiceps (Meyer). 
[Plate XV. fig. 5.] 
1844. Cobitis longiceps, L. Agassiz, Poiss. Foss. vol. v. pt. i. p. 10 
(name only). 
1848. Cobitis longiceps, H. von Meyer, Palaeoutogr. vol. i. p, 151, pi. xx, 
fig. 2. 
Type. Imperfect fish. 
A small slender species, attaining a length of about 0‘12. Length 
of head with opercular apparatus about twice as great as the 
maximum depth of the trunk and occupying slightly less than one 
third of the total length to the base of the caudal fin. Five clefts 
in snboperculum. Dorsal fin arising immediately behind the pelvic 
pair; anal fin comparatively small, arising nearly midway between 
the pelvic pair and the caudal fin. 
Form. ^ Log. Upper Oligocene : Mayence Basin. 
P. 7667. Imperfect distorted large specimen; Mombach, near 
Mayence. There are indications of the scales extending 
over the cranium; and the characteristic clefts are 
observable in the hinder border of the snboperculum. 
Purchased, 1895. 
15674. Imperfect smaller specimen; Mombach. The vertebral 
centra are shown to be slender constricted cylinders, 
which must have been pierced by a rather stout remnant 
of the notochord. About 12 rays can be counted in the 
dorsal, 9 in the anal fin. Purchased. 
P. 1820. Partly distorted fish, shown of the natural size in PI. XV. 
fig. 5; Mombach. The long and narrow cranium is 
exposed from above ; while the smallness of the mouth is 
indicated by the position of the quadrate and articular 
end of the mandible preserved beneath. The greater part 
of the characteristic maxilla is shown in impression. 
The opercular apparatus is much crushed and displaced, 
but the fissures in the suboperculum are distinguishable. 
The delicate vertebral axis is well shown, though variously 
fractured; and the extent to which the notochord 
persisted is indicated by the calcareous matrix filling the 
constricted vertebral cylinders. The very delicate ribs 
