Davis—On the Fossil Fishes of the Chalk of Mount Lebanon. 569 
This species most nearly resembles Sardinius cordieri (Osmerus cordieri, 
Agassiz), but may be distinguished therefrom by its more robust form; the 
latter has a vertebral column consisting of thirty-eight to forty vertebra, twenty- 
five of which are caudal. In this species the total number is thirty-four, of 
which only sixteen are caudal. The pectoral fin in this species appears to be 
more strongly developed than in 8. cordieri. 
Formation and Locality.—Upper Cretaceous: Sahel Alma, Mount Lebanon. 
Ex coll.—Lewis Collection; R. Damon, Esq., Weymouth, 
Genus. Opistopteryx. Picrer and Humperr. 
“Nouv. Rech. sur les poissons fossiles du Mont. Liban.,” 1866, p. 78. 
‘Body elongated, mouth largely extended; intermaxillaries straight, attaining 
nearly half the length of the maxillaries, which are the more robust; dorsal 
fin short, situated behind the middle of the body, and nearly opposite to the 
anal; ventral fins situated towards the middle of the distance, which separates 
the pectorals from the anal fin.” (P. and H.) 
Opistopteryx gracilis, P. and H. 
O. gracilis. Picrer et Humpert, 1866. ‘Nouv. rech. s. 1. poiss. foss. du Mont 
Liban.,” p. 80, pl. x1., figs. 1-4. 
Mesogaster gracilis. J. F. Picrer, 1850. ‘ Poiss. foss. du Liban.,” p. 21, pl. m1., 
fig. 2. 
Mesogaster gracilis. Fraas, Oscar, 1878. ‘Aus dem Orient. II. Theil. Geol. 
beobach. am Libanon,” p. 98. 
Formation and Locality —Soft chalk : Sahel Alma. 
Ex coll—Musée de Geneve. 
Opistopteryx curtus, Davis. 
(EL xxx) fiz, 3.) 
This beautiful little specimen exhibits the whole anatomy of the body, the 
head, and the fins. The length of the body, exclusive of the tail, is 2-1 inches; 
to this must be added 0:4 inch, the length of the tail. The depth of the body 
is 0:45 of an inch, and proportionately to the length it is as one to four and 
a-half; in this it differs from O. gracilis, Pictet and Humbert (‘‘ Nouv. Rech. sur 
les poissons fossiles du M. Liban.,” p. 80, pl. x1., figs. 1-4), in which the depth is 
one-eighth the length of the body, in each case not including the tuil. 
The head, from the tip of the snout to the pectoral arch, equals two-seventlis 
