486 DR. H. BURMEISTER ON PONTOPORIA BLAINVILLII. [May 9, 



longer a true transverse process, but only a sharp lateral crest per- 

 forated at the base by a perpendicular foramen. This perforation 

 is also seen on the sixth, seventh, and eighth vertebrae, but becomes 

 somewhat more directed to the centre of the vertebra. With the 

 ninth caudal vertebra these two perforating channels go to the cen- 

 tral part of the vertebral body, which is now only a circular piece of 

 3-4'" in thickness, somewhat more truncated on the under margin, 

 and somewbat sharper on the upper. After the fourteenth vertebra 

 I can find no more perforations, the four last being very small and 

 short nodules of decreasing size. All these, as far as the twelfth 

 from behind, are enclosed in the axis of the caudal fin. 



The animal has ten pairs of ribs attached to the dorsal vertebrae. 

 The first pair is short, only 2" 4'" long ; the largest ribs are from the 

 fourth to the eighth, each of these is 6 inches ; the last is 3" long. 

 The first four pairs have double attachments, and are divided at the 

 superior end into two prominent processes ; the lower, being the ca- 

 pitula costse, are attached to the body of the last cervical and three 

 first dorsal vertebra? ; the upper are the tubercula costse, of broader 

 but shorter extent, and attached only to the transverse processes 

 of the first four dorsal vertebrae. All the other ribs have only a 

 single superior dilatation attached to the transverse process, and cor- 

 responding to the tuberculum of the former. At the lower end the 

 ribs are somewhat broader, and truncated, and united by a small 

 cylindrical sterno-costal bone with the breast-bone or sternum. This 

 bone is composed of two distinct pieces, the anterior of broad subtri- 

 angular figure, the hinder smaller and oblong. To the very promi- 

 nent parts under the fore edges of the first is attached the first pair 

 of ribs, and near the posterior retracted edge the second pair. The 

 second oblong piece of the breast-bone is united by a cartilaginous 

 substance with the first, and bears also on each side two pairs of ribs, 

 being united with them by sterno-costal bones. The first of these 

 bones is broad and flat, and 7 lines long ; the others more cylin- 

 drical, thinner, and longer, the fourth being 1" 10'" long. The 

 fifth and sixth ribs have also sterno-costal bones, united to the end 

 of the sternum by elastic substance ; but the hinder ribs have only 

 a short incurved conical cartilaginous epiphysis. 



The bones of the anterior members or breast-fins are of the com- 

 mon cetaceous form. The scapula is triangular, with a curved 

 superior margin, 3^ inches long, and has two large anterior pro- 

 cesses above the glenoid cavity, the superior or acromion being I inch 

 long, and the inferior or coracoid process | inch. In the upper arm 

 is a very strong bone, li" long; and in the forearm the two usual 

 bones of nearly equal size, the hinder or ulnar bone being somewhat 

 more prominent at both ends. The whole carpus is cartilaginous, 

 but includes four very small spherical bones, of which the largest, 

 like a pea, is situated in front of the junction of the radius with the 

 idna, and the smallest, like a small shot, before the thumb. The two 

 others are placed between the connexions of the second, third, and 

 fourth metacarpal bones. These bones are tolerably strong ; but the 

 same bone of the thumb or first finger is extremely small, and en- 



