Davis—On the Fossil Fishes of the Chalk of Mount Lebanon. 555 
Family. HALECIDZ. Aaassiz. 
= SALMONID& + CLUPEID&. 
Genus. Osmeroides. AGAssiz. 
Osmeroides. L. Agassiz, 1834. ‘ Rech. sur les Poissons Fossiles,” vol. v., pt. 11, 
p. 103. 
Body more or less ovate, thick and depressed; head large, flat on the upper 
surface ; mouth large, with wide gape; teeth small and pointed; branchiostegal 
rays, eight on each side. Dorsal fin in advance of middle of the back, the 
base of the fin more or less elongated; pectoral and ventral fins large; anal 
moderate or small; caudal fin cleft, the two lobes equal in length. Scales 
medium or large, thin, rounded, more or less ridged on the surface, with serrated 
posterior margin. 
The genus Osmeroides was formed by M. Agassiz, and embraced three species 
of fishes from the chalk related to the sprats (Osmerus) which, with the latter, 
evidently belonged to the family of the Salmonide. In some examples traces of 
the adipose fins have been preserved; but they differ from Osmerus in being 
shorter and the peduncle of the tail being less contracted. There is also a 
difference in the positions of the fins: the dorsal is more advanced, and, instead 
of being in the middle of the back, its insertion corresponds to the anterior 
third of the back. The caudal is well developed, as are also the ventrals and 
the pectorals; but the anal is small. The skeleton much resembles that of the 
Clupea, except that it has no sternal ribs. The head is flat, as in Osmerus, 
but the mouth is smaller, and it appears that the teeth were small and closely 
set. M. Agassiz described three species, two communicated by Count Miinster, 
viz., O. monasteri and O. microcephalus, from the cretaceous formation of West- 
phalia, and one from the chalk of Lewes, O. lewesiensis; a fourth specimen from 
Lewes is referred to as O. granulatus, but not described. 
In 1850, Professor F. J. Pictet described an additional species of Osmeroides 
from Mount Lebanon (‘ Description de quelques Poissons Fossiles du Mont 
Liban.,” p. 27). He states that Osmeroides is characterized by having eight 
branchiostegal rays, which distinguish it from the Salmonide, and that the wide 
extension of the gape removes it from Coregonus. The species described by 
M. Pictet is O. megapterus. 
M. von der Marck (‘ Palzeontographica,” 1863, vol. i., p. 41), in a description 
of the fossil fishes of the chalk of Westphalia, disputes the existence of the 
adipose fin, which M. Agassiz stated he had observed on some of the Westphalian 
specimens. M. von der Marck examined more than eighty examples and could 
find no trace of an adipose fin, and this notwitlistanding that some other genera 
