williston: a new genus of fishes. 115 



amongst the Ganoids, but regards Ischyrocephaltis as a Teleostean. 

 A careful review of the whole of the genera, assisted by additional 

 specimens of Leptotrachelus and Euryophilus 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 

 peculiar arrangement of the series of scutes, and that they formed 

 a family of the Teleosteans, to which he gave the above name."* 



Cope long ago described three species and two genera of this 

 group of fishes from Dakota, which seem to have been overlooked 

 by subsequent writers. f Concerning the relationships, he says: 

 "The relationship of the family of Dercetiform fishes has been dis- 

 cussed by various authors, especially by Pictet and Von der Marck. 

 The former regards them as Teleostei; the latter as "Ganoids." 

 As I do not adopt the division signified by the last name, I find 

 Professor Pictet's view nearer to the point. The specimens indi- 

 cate further that the Dercetidae belong to the Actinopteri, and 

 probably to the order Hemibranchii. The only alternative is the 

 order Isospondyli, and the characters which separate the two are 

 not clearly shown in the specimens. Distinct bones below the pec- 

 toral fins may be interclav'cles, which belong to the Hemibranchii.'' 



The genus Triffnaspis, from the Niobrara of Dakota, there de- 

 scribed, has the dorsal and ventral scuta triradiate, the median 

 branch of the three directed anteriorly, together with numerous 

 band-like scuta. Ichthyotringa Co e, from the same locality, has 

 the body covered with small round scales. The third species is 

 Leptoiracheliis longipennis Cope, in which the dermal scuta consist 

 of median, dorsal, and ventral rows of tripodal form. 



From all these as well as other forms the present genus seems 

 amply distinct, though evidently nearest allied to Aspidopleurus 

 Pictet and Humbert, from the Lebanon Cretaceous. | This genus 

 has not been sufficiently well described to be assured of its more im- 

 portant characters, but the present form evidently differs in the 

 shape of the head, fins, sdutes, etc. 



The present fish has a curious resemblance to the Pipe Fishes. 



*Davis, on the Fossil Fish of the Cretiiceous Formations of Scandinavia. Trans. Royal 

 Dubl. Soc , iv, p. 428. 



+Bull. U. S. Geol. Surv., Terr, iv, 67. 



*Pictet and Humbert, Nouv. rech. s. les. Poissonisfossilesdu Mont Liban, p. 109, pi. 

 X, f. 1; Davis, On the Fossil Fishes of the Chalu of Mount Lebanon, Trans. Royal Soc, 

 iii, pi xxxviii, f. 4. 



