552 Davis—On the Fossil Fishes of the Chalk of Mount Lebanon. 
dichotomize. The rays extend from the body with a gentle curvature outwards 
and backwards. ‘The ventral fins are connected together by a pair of pubic bones 
joining on the abdominal surface, the fins being 0-2 inch apart. Each contains 
seven rays, of about the same length, 0°3 inch. The rays are comparatively 
strong, and the fin was capable of wide expansion. 
There is no trace of scales. 
A second specimen exhibits the caudal portion of the fish, The tail is sepa- 
rated by 0°3 inch from the dorsal fin ; it consists of a number of fine, filamentous 
rays, 0°2 inch in length, and repeatedly divided. 
Formation and Locality—Hard chalk: Hakel, Mount Lebanon. 
Ex coll—tLewis Collection, Natural History Department, British Museum 
(fig. 1); Robert Damon, Esq., Weymouth (fig. 5). 
Family. ESOCIDZ. 
Genus. Istieus. AGaAss. 
Istieus. L. Acassiz, 1834. ‘‘ Rech. sur les Poissons fossiles,” vol. v., pt. 1, p. 91. 
The genus Istieus was formed by Prof. L. Agassiz to embrace a number of 
fossil fishes restricted to the chalk, and only found in the grés-vert of Westphalia. 
Prof. Agassiz at first considered that the relationship of the genus was with the 
Scomberoids, from its external resemblance to Elacates. He failed, however, to 
discover distinct traces of spines in the rays of the dorsal fin, and a more detailed 
study of the specimens led him to doubt their existence. On the other side, the 
presence of large scales, the abdominal position of the ventral fins, the posterior 
position of the anal fins, and the form of the caudal fin, bear evident resemblance 
to the family of the Esocides, and this induced Prof. Agassiz to consider Istieus 
nearly related to that family. 
The characters which served to distinguish this genus from all other fossil fishes 
are enumerated as follows:—The vertebre are excessively short, and propor- 
tionately more numerous than in the most of the Cycloids; the iterapophysial 
bones are less numerous than the apophyses, which is not the case in any other 
fish. The dorsal fin extends nearly the whole length of the back; the anal is 
placed far backwards, so that its posterior extremity touches the base of the tail. 
The head is well developed, longer than high; the mouth small, and the jaws 
armed with small, hooked teeth. 
M. Agassiz described four species from the chalk of Baumberge, near Miinster, 
viz. Istieus grandis, I. macrocephalus, I. microcephalus, and I. gracilis. Twenty 
years later, Dr. W. von der Marck, in his elaborate and scholarly work on the 
‘‘ Fossile Fische, Krebse, und Pflanzen aus dem Plattenkalk der jiingsten Kreide 
