PHYSETEEIDJE. 67 



Choneziphius planus (Owen 1 ). 

 Syn. Ziphius planus, Owen 2 . 



This species, which is equal in size to the preceding, is referred 

 to the present genus by Gervais in the ' Osteographie des Cetaces,' 

 p. 418. The type specimen is not sufficiently perfect to admit of 

 determining whether the form described by Lankester 3 under the 

 name of C. paclcardi may not be specifically the same. 



Hab. England. 



38198. The cranial rostrum; from the Red Crag of Suffolk. This 



(Fig.) is the type specimen, and is described and figured by 



Owen, op. cit. p. 16, pi. xi. fig. 1, under the name of 



Ziphiug planus. It is also figured by Gervais in the 



' Osteographie des Cetaces,' pi. xxvii. fig. 16. No history, 



Genus MESOPLODON, Gervais 4 . 



Syn. Dioplodon, Gervais 5 . 



lielemnoziphius, Huxley 8 . 



The mandible has a single pair of laterally-compressed pointed 1 

 teeth, generally situated at some distance behind the apex. The 

 narial region of the cranium resembles that of Hyperoodon, but the 

 nasals are narrower and more deeply sunk between the premaxillse. 

 There are no maxillary tuberosities, and the rostrum is very long 

 and narrow ; in the latter the premaxillse are in contact with 

 the adjacent bones, and soldered throughout the whole length of 

 their inner surfaces ; in old specimens the mesethmoid cartilage 

 completely ossifies and forms a well-defined band on the superior 

 surface of the rostrum, whieh is solid throughout, and only shows 

 a small portion of the vomer on its inferior aspect. The posterior 

 portion of the periotic is produced and pointed, the articular ridge 

 on the tympanic aspect of the same rather low, the accessory 

 ossicle small and oval, and the anterior articular facette for the 

 tympanic deeply concave. Two or three of the cervical vertebrae 

 are united. 



1 Crag Cetacea (Mon. Pal. Soc.), p. 16 (1870). ZipUws. 



2 Loc. cit. 



3 Quart. Joum. Geol. Soc. voL xxvi. p. 502 (1870). This name i oflater 

 date than C. planns. 



4 Ann. Sci. Nat, Zool. se>, 3, Tol. xiv. p. 16 (1850). For a full synonymy see 

 Flower, ' Trans. Zool. Soc.' vol. viii. p. 208. 



5 Zool. et Pal. Francises, 1st ed. vol. ii. Exp. No. 40, p. 4 (1848-52). 



6 Quart. Journ. Geol. Soc. vol. xx. p. 388 (1864). The term was applied to 

 all the Crag forms included by Owen in Zipliius. 



T2 



