36 



BULLETIN 73, UNITED STATES NATIONAL MUSEUM. 



as the shape of the premaxillffi is similar to that found in the nominal species ger- 

 vaisii, it might be thought necessary to refer semijunctus to the latter species. As 

 will l)e shown later, however, this form of the premaxilla' appears to be charac- 

 teristic of the adult female of cavirostris, and of immatun^ individuals of either 

 sex, the young, as in many kinds of animals, resembling the adult female rather 

 than the male. 



I have been able to find but one character in the skull of semijunctus which might 

 be regarded as specific. This is that the lachrymal bone is thick distally, and cut 

 ofl" square at the end. In other specimens of Ziphius examined it is thin and flat, 

 and romided or pointed at the end. As there is much individual variation in the form 

 of the lachrymal, this peculiarity alone is, in my opinion, an insufficient indication 

 of the validitj' of the species. 



COMPARISON OF SKELETONS. 



A comparison of the skeletons of the three individuals from the Atlantic coast 

 of the United States reveals a number of differences of more or less importance. 

 Were it not for the lack of reliable differences in tlie skulls, it might be considered 

 that these variations in other parts of the skeletons indicated specific difference. 

 I am disposed, however, since the Barnegat and Newport specimens are of opposite 

 sexes, to regard them partly as sexual and partly as individual. In the case of the 

 Charleston specimen {semijunctus) , the skeleton, besides being immature, has been 

 very much damaged by careless handling, and nearly all the bones are somewhat 

 abraded. It is, therefore, only available to a limited extent for purposes of com- 

 parison. As no description of a Ziphius skeleton from the coast of the United States 

 has, so far as I am aware, been published hitherto, and as descriptions of skeletons of 

 Old World specimens are few and rather brief, I shall give below a detailed compara- 

 tive description of the American specimens. For the sake of brevity, I shall refer 

 to each specimen merely by the locality. 



VERTEBRAL COLUMN AS A WHOLE. 



The vertebral formula in the three North American specimens and in four Old 

 World specimens and Burmeister's Argentine specimen is as follows: 



Vertchral formuhi af Ziphius cavirostris. 



Locality and sex. 



Newport, Rhode Island, male 



Barnegat City, New Jersey, female 



Charleston , South Carolina, female 



Holina, Sweden (Malm) 



Pisa Museum (Van Beneden) 



Warrington, New Zealand (Scott and Parker) 



Lyttleton Uarbor, New Zealand (liaast) 



Buenos Ayres, Argentina (Burmelster), male. 



20 



1S( + 17) 

 ie(+3?) 

 18( + 1 ) 



16+ 



20 



19 



40 



40(?) 



46(?) 



40 



43 + 



46 



46 



40 



