162 Transactions. — Zoology. 



The foregoing table gives the principal measurements of the 

 vertebrae : these are in millimeters, and taken with calipers. 

 The length of the vertebra is the length of centrum mea- 

 sured from the centres of the epiphyses. The height is the 

 greatest distance from the ventral surface of the centrum to 

 tip of the neural spine. The breadth is taken from tip to tip 

 of the tranverse processes where they exist, or across the 

 widest part of centrum where the transverse processes are 

 absent. The diameters of the centrum, or body of the ver- 

 tebrae, are taken at the anterior and posterior extremities of 

 the body itself. 



It will be noted that the bodies of the vertebrae increase in 

 size up to the middle of the lumbar series, and then decrease. 

 This increase is quite gradual, but in the case of the decrease 

 in height there is a sudden drop at the end of the lumbar 

 series, owing to the sudden diminution of the neural spine. 

 The bodies of the vertebrae are much larger in the middle of 

 the vertebral column, the greater number of caudals having 

 larger centres than the thoracics, which are relatively 

 slender. 



The hinder caudals, as in other whales, are incompletely 

 formed — i.e., the neural arch is imperfectly closed above; the 

 11th caudal has no neural spine, though the right and left 

 neural laminae meet, but in the 12th they do not meet, and by 

 the 14th they are practically non-existent, so that the 15th et 

 seq. consist of centrum only. The lumbar vertebrae exhibit a 

 peculiarity, which appears to be characteristic, in the presence 

 of the anterior and posterior prominences on the ventral sur- 

 face of the centra, in the mid-line. 



I have not thought it necessary to reproduce my detailed 

 notes as to the form of the individual vertebrae. They are, on 

 the whole, closely similar to those of the sperm whale (Phy- 

 seter macrocephalus) as described by Flower ; while the gene- 

 ral appearance of the entire skeleton has been figured — more 

 or less imperfectly, it is true — by Owen, Wall, Van Beneden 

 and Gervais, and Von Haast. 



The Chevrons. — The usual form of these bones is Y-shaped 

 — i.e., each consists of a right and left lamina meeting at an 

 acute angle, and the fused plate so formed is produced down- 

 wards to form a keel. But there are variations of this type. 

 The 1st chevron is U-shaped, each lamina having an outer 

 face which is very convex; and, further, they only meet over 

 a comparatively short area, so that there is no keel. The 

 7th, again, is V-shaped, the keel being practically absent ; 

 while the 12th is a short half-cylinder of bone with a shallow 

 groove on its upper surface. It will be noticed that the 3rd 

 chevron is the largest of the series. 



