42 2 SMITHSONIAN MISCELLANEOUS COLLECTIONS [vOL. 45 



third, and fourth lower molariform teeth have their lateral diameters 

 equal to those of the anterior portions, like these teeth in Pronolagns. 

 The last upper molar is small and narrowly elliptic in section. The 

 last lower molar consists of the two usual portions, the anterior 

 larger and elliptic, and the posterior smaller and circular. 



Vertebral Coliinin. — The cervical vertebrae (pi. xcii, 2) of Romero- 

 lag us belong to the shortened type. The costal process projects 

 laterally from the centrum ; its anterior and posterior spines are 

 only moderately pronounced. The true transverse process is rather 

 conspicuous and projects laterally from the fifth cervical onward 

 through the rest of the series. 



The length of a neural spine in the anterior part of the series of 

 thoracic vertebrae is about twice the length of its centrum, relativelv 

 shorter than in .other genera. IMetapophyses are found in the last 

 three vertebrae of this series. The tenth is the anticlinal vertebra. 



The transverse processes of the lumbar vertebra (pi. xciv, 11) of 

 Ronicrolagiis are very characteristic. The processes are short and 

 wide, the longest equaling the length of the centrum to which it is at- 

 tached. The process on the first lumbar is very short and almost rudi- 

 mentary. All the processes are wide and, in general, have triangular 

 outlines. The base is broad, coming from the whole side of the 

 centrum, so that the angle between the main axis of the process and 

 the side of the centrum is completely filled up with thin bone. It is 

 an exaggeration of the condition found in Liuinolagus. The spinous 

 processes of the lumbar vertebrae are low, triangular in outline. 

 Anapophyses are very slightly developed. The first three lumbar 

 vertebrae bear hypophyses, the first of which is the shortest; the 

 second and third are nearly the same length, but the latter is a trifle 

 longer. 



The sacrum consists of the usual four vertebrae and does not 

 differ in form from the sacra of the other genera of the Leporidae. 



The caudal vertebrae of Romerolagus are only nine in number, this 

 being the smallest number of any genus except Brachylagus which 

 also has nine, and Nesolagus with eight. One vertebra is of the 

 first form, like the last sacral, five are of the second form bearing 

 more or less wing-like processes, the last three are merely centra 

 without processes. 



Sternum and Ribs. — The sternum (pi. xcvi, i) of Romerolagus is 

 very characteristic, being like that of Ochotona. The anterior por- 

 tion of the presternum is very much expanded and flattened dorso- 

 ventrally. To the outer posterior angles of this enlarged portion 

 the first pair "of ribs is attached. The rest of the presternum is long 



