MK. It. LYDEKKEK ON THE CETACEA OF THE SUFFOLK CRAG. 



15 



is intermediate between the corresponding bone of Hyperoodon and 

 that of Mesoplodon, and accords well in relative size with the 

 present genus. This bone (in which the accessory ossicle (c) is absent) 

 is nearer to that of Mesoplodon than to Hyperoodon, but approaches 

 the latter in the shortness of the posterior extremity, the large size 

 of the cavity for the accessory ossicle, and the great development of 

 the longitudinal ridge (b) on the tympanic aspect of this portion ; 

 the anterior articular facet (a) for the tympanic is also less concave 

 than in Mesoplodon. The latter genus may be taken to include both 

 Belemnozipliius of Huxley and those Crag species placed by Owen in 

 Ziphius which do not belong to Chonezipliius. With regard to species, 

 the identity of Owen's Z. medilineatus with Dioplodon Becani, 

 Gervais, of the Antwerp Crag, has been shown by the latter writer ; 

 and as my own observations in the Brussels Museum fully confirm 

 the view expressed by Du Bus as to the identity of the latter with 

 Ziphius longirostris, Cuvier (the locality of the type specimens of 

 which is unknown), I think we can have no hesitation in adopting 

 the name of Mesoplodon longirostris for this species, which agrees 

 in size with the existing M. australis. A left periotic (PI. II. fig. 8) 

 belonging either to this or one of the equal-sized species, is preserved 

 in the Jermyn-Street Museum, and is almost undistinguishable from 

 the corresponding bone of M. australis; the accessory ossicle on 

 the posterior portion of the tympanic aspect is absent in the fossil. 

 The characteristic features of the periotic of Mesoplodon are the 

 production and pointed extremity of the posterior portion, the com- 

 paratively small vertical height of the longitudinal articular ridge 

 on the tympanic aspect of the same, the small size and oval shape 

 of the accessory ossicle, and the deep transverse concavity of the 

 anterior articular facet for the tympanic. The other described Crag 

 species are M. tenuirostris (Owen), M. gibbus (Owen), M. angustus 

 (Owen), M. angulatus (Owen), and M. compressus * (Huxley); and 

 to these may perhaps be added a form of which there is a rostrum 

 in the Ipswich Museum to which the MS. name of M. Floweri has 

 been applied by Mr. Canham f . 



Squalodontidce. — The Crag Squalodon, of which there are several 

 molar teeth in the Ipswich Museum, may in all probability, as Prof. 

 Lankester suggests, be identified with the large S. antwerpiensis, 

 Van Beneden. 



Delphinidce. — The periotic of this family (PI. II. fig. 11) is distin- 

 guished by the grooving of the anterior facet (a) for articulation 

 with the tympanic, and the narrowness of the posterior tympanic 

 surface, on which the ridge for articulation with the free border of 

 the tympanic is ill-defined and situated close to one edge. The 

 occurrence in the lied Crag of an Orca considerably smaller than 

 the existing 0. gladiator is indicated by a right periotic (PI. II. fig. 9) 

 in the Museum of Practical Geology, and by an unworn and ver}' 

 perfect tooth (PI. II. fig. 10) collected by Dr. J. E. Taylor and preserved 



* Belemnoziphius compressus, Huxley, appears identical with Ziphius com* 

 pressus, Owen. 



t See Flower, Cat. Vert. Mus. E. Coll. Surg. pt. 2, p. 562 No. 2915 (1884). 



