46 SYSTEMATIC TALEONTOLOGY 



jaw: It presents "for a marked distance on the proximal portion, a 

 flat plane on the upper face, instead of the usual angulate ridge, which 

 is equally distinct from the outer and inner faces. In E. priscns the 

 superior plane is onW a continuation of the outer convex face, and 

 accordingly the external series of nutritious foramina extends along it. 

 The plane is occupied on the other hand, in the E. expansus, by the 

 inner series. 



"The inferior margin is a rather obtuse angle; the general form is 

 not compressed, nor much convex externally, as in E. priscus. 



Measurements. 



Depth ramus 2.75 in. (68 mm.) 



Thickness 1.65 in, (41 mm.) 



Foramina (internal) two in 2.50 in. (75 mm.)" 



Cope, 1869. 

 Occurrence.— St. Mary's (?) Formatiox. Mouth of the Patuxent 

 river. The type came from Nomini cliffs. 



Collection. — Johns Hopkins University. There are two rami said to 

 be preserved in the Tyson collection in the Maryland Academy of 

 Sciences. 



SiPHONOCETUs PRISCUS (Leidy). 

 Plate XXV, Fig. 5. 



Balaeva prhca Leidj-, 1851, Proc. Acad. Nat. Sci. Phila., vol. v, p. ;-!08. 

 Balaenoptera prisva Cope, 1867, Proc. Acad. Nat. Sci. Phila., vol. xx, pp. 144, 147. 

 JBalaev.opfera prisca Cope, 1868, Proc. Acad. Nat. Sci. Phila., vol. xx, p. 192. 

 Uschrichtins priscus Cope, 1869, Proc. Acad. Nat. Sci. Phila., vol. xxi, p. 11. 

 Uschrichtius priscus Leidy, 1869, Jour. Acad. Nat. Sci. Phila., 2d ser. vol. vii, p. 441 

 Cetotheriurn priscum Cope, 1890, Amer. Nat., vol. xxiv, p. 616. 

 Siphonocetus priscus Co\yQ, 189.5, Proc. Amer. Philos. Soc, vol. xxxiv, p. 140, pi. vi, 



Description. — Leidy gave the following description on the species in 

 1851 : " The fragment of lower jaw, fourteen inches long, is of much 

 more slender proportions than that of the preceding [Balaena palaeatJnn- 

 tica], it is also more uniform in its breadth and depth, and has a strong 

 curve downwards as in B. rorqual, Lac. It is very nearly flat internally and 

 demi-cylindrical externally. The upper margin is angular but not prom- 

 inent, and forms the boundary between the inner and outer side. The 



