288 



of the centrum from its posterior end, and they reach downward to the 

 middle of the sides. The bottom of the spinal canal is narrowest at the 

 middle, grooved on each side, and widens toward the ends of the centrum. 



The measurements of the specimen are as follows : Length of centrum, 

 1 inch; depth in front, 10^- lines; width, 10 hnes. 



FISHE8. 



TELEOSTEI. 



Order Acantlwpteri. 



Sphyr^nid^. 



CLADOCYCLUS. 

 Cladocyclus occidentalis. 



The genus of fishes above named was proposed by Agassiz on some remains 

 consisting of large scales and portions of a vertebral column found in the chalk 

 of Lewes, England. The name was applied on account of the branching of 

 the tube in the scales of the lateral line ; and the fish was referred to the 

 sphyreenoids. (Poissons Fossiles, V, 103 ; Atlas V, Tab. 25 a, Figs. 5, 6.) 



Some large scales, found by Dr. John E. Evans, and subsequently by Pro- 

 fessor Hayden and Mr. Meek, in ash-colored shales of the Cretaceous series 

 of Nebraska, I have supposed to belong to the same or a nearly allied genus. 

 The scales vary in form and size, and may probably belong to several species. 

 Mostly they are oval, with the length but little more than half the depth, 

 while others are circular, and these may really pertain to a different species, 

 if not genus, from the former. 



A broad oval scale, somewhat distorted and broken at the edges, is repre- 

 sented in Fig. 5, Plate XXX. The inner portion exhibits numerous radi- 

 ating ridges, while the outer portion, separated from the former by a narrow 

 smooth tract, presents a minutely tubercular or granular aspect. The depth 

 of this scale is estimated to have been nearly 2^ inches, and its length nearly 

 1^ inches. 



Another similar but less perfect specimen appears to have measured about 

 If inches wide by \\ inches long. 



A third specimen^ represented in Fig. 21, Plate XVII, has measured rather 

 more than 1 inch wide and f inch in length. 



Another scale, represented in Fig. 22, has (he same structure as the pre- 



