EXPLANATION OF THE PLATES. 



The drawings in these plates are all from nature. Those of the bones and of the 

 form of the teeth have been executed by Mr J. Dunlop Dunlop, whilst the micro- 

 socpic sections in illustration of the structure of the teeth have been made by Alfred H. 

 Young, M.B. 



Fig. 1. A profile view of the skull of the immature Mesoplodon layardi from the 

 Falkland Islands. (Specimen C.) Eeduced one-fourth. 



2. A front view of the same skull. Eeduced one-fourth. 



3. Profile view of the series of cervical vertebrae of the same animal. Reduced 



one-third. 



4. Front view of the sternum of the same animal. Eeduced one-fifth. 



5. Petrous bone of an adult Mesoplodon layardi from the Cape of Good Hope. 



(Specimen A.) Natural size. 



6. Transverse section through the beak of an adult Mesoplodon layardi from 



the Cape of Good Hope. (Specimen B.) Eeduced one-half. 



7. Inferior surface of the right tympano-periotic bone of the immature Meso- 



plodon layardi from the Falkland Islands. Natural size. 



8. Inferior surface of the right tympanic bone of a Mesoplodon, probably Meso- 



plodon layardi, dredged at Station 286. Page 37. Natural size. 



9. Inferior surface of the right tympanic bone of the ZipMus ca/virostris from 



Shetland. Natural size. 



10. Inferior surface of the right tympanic bone of a Ziphius, yi&s&mhlmg Ziphius 



cavirostris, dredged at Station 131. Page 39. Natui^l size. 



11. Outer surface of tympanic bone of a Balcenoptera, dredged at Station 286. 



Page 35. Natural size. 



12. Inferior surface of tympanic bone of a cetacean, dredged at Station 286. 



Page 36. Natural size. 



13. Inferior surface of left tympanic bone of a Kogia, dredged at Station 286. 



Page 37. Natural size. 



14. Inferior surface of a right tympanic bone, dredged at Station 286. Page 37. 



Natural size. 



15. Tooth of young Mesoplodoti layardi. Natural size. 



