34 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 03. 



Measurevients of caudal vertebrae (in millimeters.) 



Height of centrum anteriorly 63. 



Breadth of centrum anteriorly 58. 5 



Height of centrum posteriorly 53. 5 



Breadth of centrum posteriori}- 54. 



Greatest thickness of centrum 52. 



PI. 18, PI. 18, 

 Fig. 6. Fig. 7. 



58.0 

 54.0 



47.0 

 61.0 



45.5 47.5 



50. 58. 



43.5 



39.0 



Chevron hones. 



Four chevron bones were found in the matrix surrounding the 

 skeleton. One of them (pi. 18, "fig. 1) is small, elongated, and rela- 

 tively low. Another (pi. 18, fig. 2) which belongs farther back is 

 somewhat deeper and broader. The chevrons have elongated flat- 

 tened surfaces for articulation with the corresponding facets on the 

 caudals. The free margin forms a narrow posterior projection and 

 a blunt anterior projection. 



EIBS. 



The whole, or portions, of 16 ribs are preserved. Only one of the 

 ribs was found associated with the corresponding vertebra ; the others 

 lay in a tangled pile alongside of the anterior lumbars. Eight of 

 them (pi. 10) were left imdisturbed when the slab in which they 

 were imbedded was prepared for exhibition; the others were freed 

 from the matrix. 



This fossil porpoise possesses 10 ribs on each side, of which the 

 first is the shortest. The ribs rapidly increase in length from the 

 first to the sixth (pi. 16, fig. 5), which is the longest, and then de- 

 crease in length to the tenth (pi, 16, fig. 7). The couA^ex external 

 curvature of the shafts of the three anterior ribs is less pronounced 

 than in the others ; this curvature rapidly increases posteriorly, reach- 

 ing its maximum development in the fifth, sixth, and seventli ribs. 

 The curvature of these last-mentioned ribs is very nearly the same. 

 All of the ribs show at their distal end provision for the attachment 

 of cartilages. The capitula of the first to the seventh ribs are borne 

 upon long necks and the length of the necks increase as we go back- 

 ward along the series to the seventh. On the eighth, ninth, and 

 tenth ribs the capitulum and tuberculum are fused with each other. 



The first seven pairs of ribs have capitula articulating with the 

 centra, as well as tubercula articulating with the transverse pro- 

 cesses ; in the three posterior ribs, however, the articulation is limited 

 to the transverse process. Four pairs of ribs are connected by carti- 

 lage with the sternum in Platanista and similar relations may have 

 been maintained in this fossil porpoise. 



The first three ribs are greatly compressed and their proximal por- 

 tions are bent at right angles to the shafts. The first rib (pi. 16, fig. 1) 

 is short, flattened, and thickest at its distal extremit}^ ; the capitulum 



