CETACEA. 71 



On the inner side (fig. 0), running from end to end, is seen the 

 fissure which was occupied by so much of the mesethmoid cartilage 

 as remained unossified. The sides and lower edge of this fissure, 

 where they have been in contact with the cartilage, are smooth 

 and longitudinally grooved ; but the upper surface is rough and 

 deeply pitted, evidently indicating an edge of cartilage gradually 

 undergoing ossification. The rough surface extends backwards 

 for about 12 inches, at which point the roof of the fissure descends 

 and meets the floor, leaving a slight opening at the side. Behind 

 this the roof is formed of broken cancellous bone, and it seems 

 probable that a median bony septum occupied the whole of this 

 hinder part of the cavity, thus obliterating the fissure, with the 

 exception of a mere film of cartilage, or membrane, on each side. 

 Some of the specimens of C. planirostris in the British Museum 

 seem to have the hinder part of the mesethmoid region similarly 

 ossified ; and thus when viewed from behind this region appears as 

 completely ossified as in Mesoplodon ; but although a portion of 

 the upper part of this cartilage has been ossified throughout its 

 length, yet the lower part of the anterior 12 inches remained 

 cartilaginous in this specimen. To what extent the side walls of 

 the fissure are due to ossification of the mesethmoid it is difficult to 

 say, but certainly the conformation at the back closely resembles 

 that found in Mcsoplodon, and appears to indicate that the median 

 mass is really the mesethmoid, which, however, never seems to 

 reach the upper surface of the rostrum ; but is overlaid by the 

 premaxillae ; no information on this point can be obtained from 

 Mr. Philps' specimen, which is, unfortunately, imperfect at the 

 hinder part of the premaxillary region. 



CHONEZIPHIUS PLANUS, OWEN. 



This species was originally described by Sir R. Owen (Pal. 

 Soc. 1870, p. 16) under the genus Ziphius, the type being a much 

 denuded specimen, from the Red Crag of Shotley, Suffolk, pre- 

 served in the British Museum (Cat. Foss. Mamm., Part v, p. 67, 

 1887) and it was referred to the genus Choneziphius by Profs. 

 Van Beneden and Gervais (Osteogr. Cetaces, p. 418, 1880). 



CHONEZIPHIUS PACKARDI, LANKESTER. 



Choneziphius Packardi was established by Prof. Lankester 

 (Quart Journ. Greol. Soc., Vol. XXVI., p. 502, PI. xxxiv, 1870) 

 for the reception of a rostrum from the Red Crag Nodule-bed of 

 Felixstow, preserved in the Ipswich Museum. Mr. Lydekker 

 suggests the possibility of this species being identical with the 

 C. planus (Quart. Journ. Geol. Soc., Vol. XLIIL, p. 14, 1887). 

 The type specimen of the latter, however, is too imperfect to 

 admit of comparison. 



