Davis — On the Fossil Fish of the Cretaceous Formations of Scandinavia. 429 



ramplius, and Von der Marck also places tlie genera Pelargorhynchus and 

 Leptotrachelus amongst the Ganoids, but regards Iscliyroceplialus as a 

 Teleostean. A careful review of the whole of these genera, assisted hj additional 

 specimens of Leptotrachelus and Eurypholis discovered in the chalk of Mount 

 Lebanon, convinced M. Pictet that they formed a group naturally associated, 

 especially by the great analogy afforded by the pecuKar arrangement of the 

 series of scutes, and that they formed a family of the Teleosteans, to which he 

 gave the above name. 



Genus. Dercetis. Agassiz, " Rech. sur les Poissons Fossiles," vol. ii., pt. ii., 

 p. 258, pi. Lxvi.a, figs. 1, 2, 5, 6, 7, 8 [iion figs. 3, 4). 



8yn. — Leptotrachelus, . . V. de Marck, 1863-64. " Fossile Fische, Krebse 



und Pflanzen aus dem Plattenkalk der jting- 

 sten Kreide in Westphalen." — Palseonto- 

 graphica, vol. xi., p. 59. 



Leptotrachelus, . . Pictet et Humbert, 1866. " Nouv. Rech s. les 



Poissons Fossiles du Mount Liban.," p. 93. 



Leptotrachelus, . . Davis, 1887. " On the Fossil Fishes of the 



Chalk of Mt. Lebanon."— Trans. Roy. Dub. 

 Soc, ser. II., vol. iii., p. 619. 



The genus Dercetis was instituted by M. Agassiz, in concert with Count 

 Miinster, for fossil fishes, with elongated body and head, the latter prolonged into 

 a straight beak. The upper jaw a little longer than the lower, both being armed 

 with elevated conical teeth, alternating with others smaller. The spinal column 

 composed of robust vertebrae, longer than high, and constricted in the middle. 

 Pectoral fins large, the ventrals small and composed of few rays. The dorsal fin 

 is described as extending along nearly the whole surface of the back, the anal 

 being about half the length of the dorsal, and finishing at the same point. The 

 caudal short and slightly forked. The sides of the body are furnished with three 

 rows of scutes, extending the whole length, and resembling those of the sturgeon. 

 The scutes are heart-shaped, osseous, with a granular external surface, and 

 surmounted by an angular median projection. The species described as pertain- 

 ing to this genus are D. elongatus, Ag., from the chalk of Lewes, England, and 

 D. scutatus, Miinst. and Ag., from the Chalk of Westphalia. Mr. A Smith "Wood- 

 ward * has already pointed out that the English specimens are entirely devoid of 

 fins ; and it may consequently be presumed that the description of the long dorsal 

 and anal fins was taken from the Westphalian species. It may further be inferred, 



* " Proc. Geol. Assoc," vol. x., p. 318. 1888. 



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