AND AFFINITIES OF POTAMOGALE. 9 



becomes separated by a wide interval from the metapophysis, and then disappears on 

 the first lumbar. No diapophyses are developed on the fifteenth and sixteenth dorsal ; 

 but they reappear on the first lumbar, and constitute broad, flat processes, directed 

 downward and outward and a little forward, on all the lumbar. The diapophysis of 

 the first lumbar is terminated by a flat, nearly square pleurapophysis, which appears 

 as a simple continuation of the diapophysis, but whose line of junction with it still 

 remains distinct. 



The nem-al spine of the first dorsal is nearly vertical, long, and slightly compressed ; 

 those of the second, third, and fourth are equal to it in length, and of a similar form, 

 but incline more backwards, the inclination gradually increasing to the fourth ; from 

 the fifth to the tenth, the neural spines are stiliform, gradually decreasing in length, 

 and incline so much backwards that the anterior rests upon the posterior; and the 

 vertebrae here present a remarkably imbricated appearance ; from the eleventh to the 

 thirteenth, the neural spines are shorter, and incline less backwards ; they then assume 

 the form of laterally compressed vertical plates, gradually increasing in size to the fii-st 

 lumbar, whence they continue of nearly the same form and size to the fifth lumbar. 

 From the body of the first dorsal a small hypapophysis is developed ; it becomes some- 

 what larger on the second, third, and fourth, is reduced to a nearly obsolete keel on 

 the fifth, and then entirely disappears. 



The ribs are sixteen in number, of which the first nine articulate with the sternum ; 

 the remainder are free. The fii'st is the shortest and stoutest ; its cartilage is broad 

 and flat, and articulates with the manubrium ; of the remaining ribs, the last two arti- 

 culate with the bodies only of their respective vertebrae, while the others articulate 

 also with the transverse processes. The sternum is composed of eight pieces: the 

 manubrium is spade-shaped ; from the second to the sixth, they form quadilateral prisms, 

 gradually decreasing in length and increasing in breadth; the seventh is nearly cubical, 

 with two surfaces posteriorly for the articulation of the cartilage of the eighth pair of 

 ribs ; the eighth piece is long and appressed, and carries the small xiphoid cartilage on 

 its extremity. 



8acral and caudal Regions.— There are three sacral and thirty-thi-ee caudal vertebra, 

 the ossa innominata being united to the first and second sacral. The neural spines, 

 metapophyses, and diapophyses continue to be well developed on the sacral and for 

 some distance on the caudal vertebra;; they then gradually diminish on the caudal 

 vertebrae with the diminishing size of these, until towards the end of the tail they dis- 

 appear, and the vertebra; become reduced to minute centra. All the caudal vertebrae, 

 from the second to about the twenty-third, are provided with chevron bones : towards 

 the proximal end of the tail these bones are remarkably large ; they then gradually 

 diminish in size, and become mere rumdients before their final disappearance. They 

 are each articulated m an intervertebral space ; most of them develope a short haemal 

 spine, and send off at each side from their lower surface a broad horizontal plate. 



VOL. VI. PART I. •'" 



