TRANSACTIONS OF SECTION D. 681 



wliile allowing five prre-caudal vertebrae for a sacral series, tliere is much 

 variability regarding the position of the first sacral segment. Thus, among cer- 

 tain Mystacoceti, it would occur from the 27th to the 31st vertebra behind 

 the skull, but in Balfenoptera sibbaldii at the 33rd or 34th. Among toothed 

 whales (Denticeti) the variability is much greater, especially among Deiphinidfe, 

 not only in different species, but even in different specimens of the same species 

 and in diff'ereut sexes, for the first sacral vertebra may be situated from the 27th 

 to the 43rd vertebra behind the skull. 



Notwithstanding these differences, the position of the pelvic organs indicates 

 that they are due rather to variation iu the number of dorsal and true lumbar 

 vertebrae than to increase in the length of the sacral region. Therefore, from the 

 position of the pelvic organs and the presence of a peritoneal cavity (pelvic) iu 

 Cetacea, and also the common occurrence of five vertebrae in the sacrum of quadru- 

 pedal mammals, the authors believe that among Cetacea five prae-caudal vertebr:e 

 might fairly be classified as sacral, or, conversely, that the sacral series of vertebrre 

 might be reckoned from the inlet of the peritoneal pelvic cavity to the first of the 

 chevj'on-bearing- or caudal vertebra}. 



2. The Eelationshi2os of the Premaxilla in Bears. 

 By Richard J. Anderson, M.D., Professor of Nahurcd History, Galtcay. 



The premaxilla presents many features of interest because of its relations to 

 other bones in the same animal, and to the same bone in other animals, also because 

 of the peculiar po.sition which was assigned to it in the vertebrate theory of the 

 skull. 



This bone in the bears articulates with the frontal, and differs in this respect 

 from the position of the bone in other carnivora. The following summary repre- 

 sents the facts in the species examined : — ■ 



JJrsus 2)yrenm(s. — The distance from the alveolar margin of the premaxilla 

 to the nasal in the middle line is 2f inches. The naso-premaxillary suture is 



3 inches in length, The premaxilla 1 inch wide below by 3| inches in length. 

 The nasal is 3 inches and the maxilla 3f inches. The maxilla is thus shut "out 

 from the nasals. 



Ursus labiatus.— The length of the skull here is 1 foot and the premaxilla 



4 inches. The premaxilla is nearly ^i inch across at the lower end of the 

 nasals. The measurement from the incisor alveolar margin to the lower border 

 of the nasals is 2;^- inches. The naso-premaxillary articulation is 2 inches in 

 length. 



Ursns arctos. — The length of the skull is 1 foot 2 inches; nasals, 3^ inches 

 by i inch broad ; premaxilla, 4^ inches long by f inch broad. Tliis may 

 be compared with the last. The distance of the alveolar margin from the 

 lower border of the nasals is 2f inches. It is 1 j inch from the nasal edge to 

 the point of articulation with the frontal. The naso-premaxillary suture is 

 2^ inches. Brown bear has a naso-maxillary suture (Owen). 



The premaxilla of the Himalayan bear reaches further up and back than in 

 Ursus arctos and U. labiatus. Alveolar margin to nasal is 2:i- inches; naso- 

 premaxillary suture. If inch ; premaxillary maxillary suture, 3f inches. 



_ Heliarctos has a skull 1 foot iu length. The nasal is 3 inches and premaxillary 

 4 inches long. The alveolar margin is 2^- inches distant from the nasals. The 

 naso-premaxillary suture li- inch. 



Ursus maritimus has nasals 4 inches long and premaxillae 5 inches. The 

 nasals appear to reach higher than usual. The distance of the lower border of 

 nasals from the alveolus is 3^ inches; the naso-premaxillary margin is 1| inch. 



The fen bear, an ancient variety of Ursus arctos, Avhich is sometimes found 

 in Irish bogs, has a premaxillary maxillary suture 'ih inches long, and naso- 

 j)remaxillary 1^^ inch (a little less than in "U. maritimus) ; the alveolar margin 

 to nasal, 2f inches. This and other specimens were kindlv placed at my dispolial 

 in the Kildare Street Museum, Dublin. 



