14 Mr. W. S. MacLeay on the Comparative Anatomy 
to the whole spine, the irregularity of the number of vertebrze is 
so great, that even neighbouring species,—such as the dog and 
wolf, the camel and dromedary, the horse and quagg ga,—differ 
widely in number. Nay more, the same species sometimes 
presents a variety of number in the vertebral joints. The dif- 
ference, moreover, between the maximum numbers of vertebrae 
in Mammalia and birds, as hitherto observed, is 17 in favour of 
Mammalia ; while the ditference between their respective mini- 
mum numbers, as hitherto observed, is 9,--Mammalia having 
also the least. Hence, according to what has been said, the 
differences of the number of vertebre in Mammalia is of much 
less consequence, as connected with natural arrangement, than 
those in birds. te "den 
Now let us watch the general variation of the EE of 
spinal vertebræ in birds; for which purpose I must construct 
my tables upon the data afforded by those which are given by 
M. Cuvier in his Leçons d' Anatomie Comparée, although I am 
far from conceiving them to be correct. ` 
Number | Maximum num- | Minimum num- | Extent 
Orders. of species |ber of vertebrze in|ber of vertebrze in of ` Observations. 
examined. the spine. the' spine. variation. 
1. Rarronms a pocas BG, TT 
i = 3 : ; n into account, be- 
2.IwsEssonEss .| 21 - + Be 99- —HL -9- cause Cuvier does not give 
Pica. Loxia. the number of Soer gian 
Cb vertebrae. 
3. RasorEs .. 7 55 37 18 
Struthio. Meleagris. — 
Hemantopus is excluded, 
: ; because Cuvier does not 
4. GRALLATORES| 13 - rs F = 39 7 give the number of verte- 
olopax. umenius, bræ in the coccyx: 
x: Petrel is not included, 
i i ; z ecause Cuvier does not 
5. Natatores .| 12 " 56 89 17 giyo Abe set OF sacral 
. V ygnus. Larus. vertebra, 
Hence, 
