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XV. On the Vertebrate Skeleton. By Sv. GEORGE MIVART, F.R.S. 
(Plate LIIL.) 
Read April 21st, 1870. 
THE paper which I have now the honour of submitting to the Linnean Society, is an 
endeavour to throw, if possible, a little additional light on relations believed to exist be- 
tween certain subordinate portions of the vertebrate skeleton. 
In order to attain this object I am compelled to make certain general observations on 
the skeleton as a whole, and upon the different ways in which its component parts may 
be regarded. ; i 
The term! “skeleton,” in its broadest sense, may be considered to denote that system 
of structures which invests and supports the whole frame; but it is generally and con- 
veniently taken to mean such parts of that system as assume (at least occasionally and 
in some animals) a cartilaginous or osseous condition. 
The skeleton, so restricted, is generally considered to be divisible into two categories, 
namely :—one external, comprising dermal and epidermal structures—the exoskeleton ; 
the other internal, and thence termed the endoskeleton. 
'The endoskeleton consists of a greater or less number of temporarily and permanently 
distinct parts; and these parts may be distinguished, grouped, and classified in as many 
distinct ways as there are distinct modes of regarding them. Thus they may be re- 
garded :— : 
1. Teleologically, or according to the use, object, or application of parts, or groups of 
parts—as when we say “a wing-bone ” or a “ brain-protecting part.” 
2. According to shape and outline of parts—as when we say “a long bone,” as in 
speaking of the tibia. 
3. Histologically, or according to structure—as when we speak of “ cartilaginous parts 
of the skeleton,” or, again, of bones ossified from membrane (like the frontal), or from 
cartilage (like the basioccipital). 
4. Developmentally, or according to the way parts arise—as when we speak of “ skeletal 
structures developed in the dorsal plates of the embryo.” 3 
5. Specially, or according to the relation parts in one animal bear to parts in another 
animal—as when we speak of the alisphenoid of a bird and of a reptile. 
6. Genetically, or accordingly as the resemblance between similar parts in different 
animals is due to inheritance from a common ancestor, or has arisen independently 
through similarity of conditions. E 
7. Serially, or according to the relation parts of an animal bear to other parts, in 
front of or behind them, in the same animal—as when we speak of “the last rib but one.” 
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