lyon] the hares and their allies 341 



On the other hand, in certain hares, the distinctness of the inter- 

 parietal is lost at an early age, when the animal is but little more 

 than half grown. Judging from rather limited material in cases 

 where its distinctness is lost in the adults, it appears that the upper 

 borders of the bone become obliterated, each half fusing with the 

 parietal above, and the sagittal suture between the two parietals 

 pushing down to meet the interparieto-supraoccipital suture. The 

 distinctness or the obliteration of the interparietal is very constant, 

 for the different groups of the Leporidse. It is found as an inde- 

 pendent bone in Sylvilagus, Brachylagus, Limnolagus, Oryctolagus, 

 Roiiicrolagiis. In the genus Lepiis, the interparietal loses its dis- 

 tinctness before adult life is reached. In the single available skull 

 of PronoJagiis from South Africa, the inferior suture of the inter- 

 parietal is distinct, as it always is ; the right latero-superior suture is 

 partially obliterated, and the left latero-superior suture is entirely 

 obliterated. As the specimen is a young adult, it seems reasonable 

 to say that the interparietal is obliterated in this case. In the genus 

 Pcufalagus the interparietal is not present as a distinct bone. 



palate and posterior nares 



The' bony palate of all the Leporidse has its antero-posterior 

 dimension very short, while the side-to-side dimension is consider- 

 able, so that the length of the bony palate is usually less than its 

 width. The palatal portion of the bony palate is the part most re- 

 duced, and in some cases the horizontal plates of the palate bones 

 form only the extreme posterior edge of the bony palate. The 

 incisive foramina are very large, especially at the posterior ends, 

 and extend from the anterior edge of the bony palate almost to 

 the alveoli of the incisors. The roof of the narial cavity is usually 

 high, so that the sides of the posterior nares form a wall of con- 

 siderable height, composed mostly of the vertical portion of each 

 palate bone. All of these structures vary in several ways and con- 

 stantly for certain groups. 



Variations in bony palate. — In Bracliylagus the bony palate is 

 very short, shorter than in any other genus of the Leporidje. The 

 horizontal plates of the palate bones form only the posterior border 

 of it. In Lepiis also the palate is short, but not so short as it is in 

 Brachylagus. The horizontal plates of the palate bones form be- 

 tween a fourth and a third of the bony palate. Very similar to this 

 arrangement is the bony palate of the genus Syh'ilagus, which is 

 typically a little longer than it is in Lcpus, but in the rabbits of the 

 Sxh'ilagns ari:;oncc group the bony palate has about the same relative 



