184 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



of the river from Leavenworth, Kansas, near Weston, in Platte County, Mis- 

 souri. The name by which it may be designated has reference to the inter- 

 mediate characters which it displays between Orodus and Campodus. The 

 coronal surface is elevated into a median prominence, and is marked with the 

 longitudinal and transverse ridges which are so conspicuous a feature of Orodus, 

 but at the same time the outer coronal margin, which at the most is only 

 faintly crenulated in other species of Orodus, is here differentiated after the 

 manner of Campodus. It is obvious that the two genera are very closely 

 related, but the characters by which they may be provisionally distinguished 

 appear to warrant their separation, at least until such time as we shall have 

 obtained a more perfect knowledge of the arrangement of the dentition in both 

 forms. 



Formation and Locality. — Missouriau ; Missouri Kiver Valley. 



CAMPODUS OE KONINCK. 



Campodus variabilis (Newberry and Worthen). 

 (Plate 1, Fig. 1; Plate !J, Figs. 15, 16.) 



1870. Lophodus variabilis Newberry and Worthen, Pal. Illinois, Vol. IV., p. 361, 



PI. IV., Figs. 4, 5, 11. 

 1875. Agassizodus variabilis St. John and Worthen, Op. cit. Vol. VI., p. 318, PL, 



VIII., Figs. 1-22. 

 1883. Agassizodus variabilis M. Lohest, Ann. Soc. Geol. Belg., Vol. XL, p. 305, 



Text-figs. 1, 3. 



1901. Campodus variabilis C. R. Eastman, Science, Vol. XIV., p. 795. 



1902. Campodus variabilis C. R. Eastman, Geol. Mag. (4), Vol. IX., p. 148, PI. 



VIII., Fig. 1. 

 1902. Campodus rariabilis C. R. Eastman, Bull. Mus. Comp. ZooL, Vol. XXXIX., 

 p. 57, Pis. I. II., PI. IV., Fig. 1. 



Detached teeth of this species are of not infrequent occurrence in the Mis- 

 sourian of Iowa, Kansas, and Nebraska, and in two or three instances a large 

 part of the dentition has been found in natural association. The complete 

 dentition of one jaw (presumably the lower) is known from a series of inter- 

 esting specimens, the most important of which was first described by St. John 

 and Worthen in Volume VI. of the Palaeontology of Illinois, and has been 

 since re-investigated by Max Lohest and the present writer. The original of 

 this magnificent specimen is now preserved in the private collection of Mr. 

 Frank Springer, and casts made from it by St. John in 1874 are in existence 

 in a number of museums. One of these plaster casts was utilized in the 

 construction of the model shown in Plate 1, which represents the restored 

 dentition, the symphysial series in front being photographed from an actual 

 specimen belonging to the Museum of Nebraska State University. 



The nearly complete ramus of the lower jaw described by St. John and 



