PROFESSOR FLOWER ON THE RECENT ZIPHIOID WHALES. 223 



that in life the tooth was entirely concealed'. The height of the right tooth from 

 the middle of the base to the apex is 1'8 inch, the length of the base is 1"1 inch, 

 the length of the anterior margin is 1"5 inch, of the posterior margin 2 inches, the 

 greatest thickness 0'6 inch. The left tooth is slightly larger than the right. 



A longitudinal section in the antero-posterior direction having been made through 

 these teeth, their structure was seen to be very similar to that of Mesoplodon sowerhyi, 

 as described by Mr. E. Ray Lankester^. In the larger anterior tooth the only remains 

 of the pulp-cavity is a small irregular vacuity {p), an inch below the apex of the tooth, 

 and consequently more than an inch and a half from the base. The true dentine {d) is 

 limited to the portion of the tooth above this spot, the large bulk of the tooth below 

 being composed of very coarse-looking osteo-dentine with numerous wavy fissures and 

 channels, having a general longitudinal direction ; immediately around the pulp-cavity 

 a tissue {g) having a botryoidal or globular arrangement forms a transition from the last- 

 named structure to the true dentine. There is no enamel. The surface of the tooth, 

 except at the apex and base, is covered with a layer of cement {(■), which nowhere 

 exceeds y,^ inch in thickness. The constituent elements of the smaller tooth are 

 arranged in a precisely similar manner. 



Hyoid hones. — The basihyal and the thyro-hyals are not yet united (PI. XXVIII. 

 fig. 9). The former is more elongated transversely than in Hyperoodon, being 5"8 inches 

 in width, and 2-7 inches in antero-posterior length at the middle. The posterior 

 border is straight ; the anterior border excavated in the middle, and with a roughened 

 prominence near each end for the attachment of the anterior comua. 



The thyro-hyals are each 9 inches long, and 2"5 inches in greatest diameter. Their 

 under surface is flattened. They are less wide in proportion to their length than in 

 Hyperoodon, and thus, as in so many other details of the skeleton, they show that Berar- 

 dius recedes further from Physeter than does that genus', and consequently approaches 

 nearer to the ordinary Dolphins, 



The stylo-hyals are 14 inches long, and 2'9 inches in greatest thickness, slightly 

 curved, and with three distinct surfaces bounded by three longitudinal ridges, the 

 broadest and flattest surface being in the concave side of the bone. Towards what 

 appears to be the upper end there is a neck-like constriction, surmounted by an 

 expanded and obliquely truncated head. 



Vertebral Column. — The numbers of the vertebrae are : — cervical 7, thoracic 10, 



' See the remarkable observations upon the teeth of the animal when aUve, recorded by Dr. Haast (p. 214), 

 and the mention of " muscular bundles " by which they are moved by Dr. Hector (p. 216), which accord so 

 little with any thing hitherto known in mammalian anatomy, that further observations on this subject are 

 extremely desirable. 



- Transactions of the Royal Microscopical Society, new series, vol. xv. 1867, p. 55. 



^ The breadth and flatness of the thyro-hyals is eminently characteristic of both the genera of Physeterinae, 

 Physeter and Eogia : and the affinity of the Ziphiinae to them is in this respect only slightly marked, though 

 most 80 in Hyperoodon. 



