14 MR. R. LYDEKKER ON THE CETACEA OF THE SUFFOLK CRAG. 



that of Physeter, and thus, if rightly referred, confirms the generic 

 distinctness of the present form from the latter. The small Homo- 

 cetus Villersi, Du Bus, is, I believe, represented by a tooth from the 

 Eed Crag, in the British Museum (No. 49966), and not improbably 

 by other teeth in the Ipswich Museum. 



I now come to the genus Balcenodon, Owen, which was founded 

 upon an imperfect tooth, whose affinities have given rise to much 

 discussion *. In describing the type specimen, Owen regarded it as 

 a segment of a complete tooth, and described the central axis as 

 dentine, and the outer coat as cement ; but a comparison with teeth 

 in the Brussels Museum, to which Du Bus applied the name of 

 Scaldicetus Carreti, has shown that the cement has entirely dis- 

 appeared, and that the axis is really the ossified pulp-cavity, and 

 the outer coat the dentine. The English specimen is specifically 

 identical with the Belgian ones, and the name Baloenodoyi must 

 therefore supersede Scaldicetus. The complete teeth of the genus 

 have their crowns tipped with enamel. Of the allied but smaller 

 genus Physodon t, Gervais, there are teeth in the British Museum 

 from the lied Crag corresponding to those of P. grandis (Du Bus), 

 while one imperfect tooth (No. 44109) may not improbably belong 

 to P. fusiformis (Du Bus). The genus Hoplocetus comprehends 

 other Physeteroids with enamel-tipped teeth, which are characterized 

 by the excessive thickness of their cement and the presence of a. 

 constriction at the base of the crown. Certain worn (and pro- 

 bably derived) teeth from the Bed Crag in the British Museum and 

 other collections appear to indicate the occurrence of the Miocene 

 H. crassidens, Gervais, while others may be referred to the Diestian 

 H. borgehoutensis, Gervais, and others, again (more doubtfully), to 

 E. curvidens of the same epoch. 



In the Ziphiine subfamily Hyperoodon is represented by a very 

 perfect right periotic from the Bed Crag in the Ipswich Museum 

 (PI. II. fig. 6). This specimen, which has the accessory ossicle (c) still 

 attached, cannot be distinguished from the corresponding bone of 

 the existing rostratus, and evidently indicates the existence either 

 of that or of a closely allied form in the Pliocene ; the occurrence of 

 cervical vertebras of a member of this genus in the Antwerp Crag has 

 been recorded by Prof. Van Beneden J. The genus Choneziphius, 

 which appears to be in some respects intermediate between Hyper- 

 oodon and Mesoplodon, and differs from the latter by the non- 

 ossification of the supravomerine cartilage, is represented by the 

 typical C. planirostris (Cuv.). The so-called Ziphius planus, Owen, 

 also belongs to the same genus, but the type specimen of that species 

 is not sufficiently perfect to determine whether Clionezipldus Packard'^ 

 Lankester (which is of rather later date), is really entitled to specific 

 distinction. I refer to this genus a left perioti 0 (PI. II. fig, 7) from 

 the Eed Crag, preserved in the Museum of Practical Geology, which 



* Gervais identified Balcenodon with Hoplocetus, while Van Beneden and 

 Lankester thougnt it might be a Squalodon. 

 t Syn. JPalcBodelphis Du Bus. 

 X Bull. Ac. E. Belg. ser. 2, vol. x. p. 407 (1860). 



