Zoological Society. 469 



9 fl 2 + C 9 « 2 — c 9 , N 



^ * = cos — » ) 



" — 2 2 



Thus for uniaxal crystals where i t -f » = 80 

 t;* = a 2 



u,/ 2 = a 2 . (cos /) 2 + c 2 (sin ») 2 . 

 [To be continued.] 



LXV. Proceedings of Learned Societies. 



ZOOLOGICAL SOCIETY. 



Dec. 13, A Paper was read by William Ogilby, Esq., with a view 

 1836.* <£*- f pointing out the characters to which the most im- 

 portance should be attached in establishing generic distinctions among 

 the Ruminantia. 



Mr. Ogilby commences by observing that " It has been justly re- 

 marked by Professor Pallas, that if the generic characters of the Ru- 

 minantia were to be founded upon the modifications of dentition, in 

 accordance with the rule so generally applicable to other groups of 

 Mammals, the greater part of the order would necessarily be comprised 

 in a single genus ; since the number, form, and arrangement of the 

 teeth being the same in all, except the Camels and Llamas, these 

 organs consequently afford no grounds of definite or general distinc- 

 tion. Hence it is that naturalists have been obliged to resort to other 

 principles to regulate the distribution of ruminating animals ; and the 

 form, curvature, and direction of the horns, selected for this purpose 

 at a period when the extremely limited knowledge of species permitted 

 the practical application of such arbitrary and artificial characters 

 without any very glaring violation of natural affinities, still continue 

 to be the only rule adopted by zoologists in this department of Mam- 

 malogy. The illustrious Illiger forms a solitary but honourable ex- 

 ception ; he first introduced the consideration of the muzzle and la- 

 chrymal sinus into the definitions of the genera Ant Hope, Copra, and 

 Bos ; but his labours were disregarded by subsequent writers, or his 

 principles applied only to the subdivision of the genus Antilope. It 

 is obvious, however, that as the knowledge of new forms and spe- 

 cies became more and more extensive, the prevailing gratuitous rule 

 above mentioned, founded as it is upon purely arbitrary characters 

 which have no necessary relation to the habits and oeconomy, or even 

 to the general external form, of the animals themselves, would even- 

 tually involve in confusion and inconsistency the different groups 

 which were founded upon its application ; and such has long been 



* The preceding papers read at this meeting have been noticed in the 

 present volume, p. 196. 



