- ON THE VERTEBRATE SKELETON. 183 
ratory currents, and in the prehension and deglutition of the food. Cuvier 
himself regards in the same light the analogous subdivision of the mandibular 
or lower half of the arch, and both Conybeare* and Bucklandt have well 
illustrated the final purpose which the subdivision of the lower jaw of the 
‘Crocodile into overlapping pieces, subserves. Cuvier has given distinct and 
convenient names to these several pieces of the mandible, but he views them 
collectively as answering to the simple mandible of the mammal and the bird. 
I, in like manner, regard the subdivided pedicle supporting the mandible in 
fishes as answering to the undivided pedicle supporting the mandible in ophi- 
‘dians, lizards and birds. ‘There is the same necessity or convenience for a 
distinct name to each distinct part of the tympanic pedicle, or upper part of the 
tympano-mandibular arch, as for the divisions of the mandible or lower part of 
that arch. But Cuvier unfortunately persuaded himself that the subdivisions 
of the tympanic pedicle in fishes represented other bones in higher vertebrates 
besides the tympanic, and applied to them the names of such bones. I have 
been compelled, therefore, in dissenting from this view to propose new names 
for the peculiar ichthyic subdivisions of the tympanic, and in doing so I have 
been careful to retain the dominant term, and to distinguish the parts by 
prefixes indicative of their relative position. Time and the judgement of 
succeeding homologists will determine the accuracy or otherwise of this 
view; and, should it be ultimately adopted, I feel great confidence that the 
terms ‘epitympanic’ (epitympanicum, Lat., fig. 5, 282), mesotympanic (meso- 
tympanicum, 2b), pretympanic ( pretympanicum, 2sc) and hypotympanic 
(hypotympanicum, 23d), will be preferred to the names proposed by Geoffroy 
St. Hilaire for the same parts. With regard to the subdivisions of the man- 
dible in cold-blooded vertebrates, I adopt most of those proposed by Cuvier. 
As, however, ‘operculaire’ had been applied by the great anatomist toa 
distinct bone in fishes, it was necessary, in order to avoid its use in a double 
sense, te substitute a distinct name for the part of the jaw in question, and as 
it is always applied, like a surgeon’s splint or plaster to the inner side of most 
of the other pieces, that of ‘ splenial’ (splenium, Lat., figs. 22,23, 31) suggested 
itself to me as the most appropriate name. For an obvious reason I have 
restored the term ‘ coronoid’ (coronoicewm, 31') in place of ‘ complementary,’ 
for the piece into which the crotaphite muscle is always more or less inserted 
in the mandible of reptiles. There isno ground for disturbing the appropriate 
names given by Cuvier to the parts of the diverging appendage of the tym- 
pano-mandibular arch in fishes; and the same principle which he has adopted 
in distinguishing the different opercular bones (fig. 5, 31-37), has guided me 
in naming the different parts of the bony pedicle which supports them. 
I have gladly adopted as many of the well-devised terms which Geoffroy 
proposed for the elements of the hyoid arch, as his unsteadiness in their ap- 
plication would permit to be retained. They are obviously preferable to the 
descriptive phrases by which Cuvier designates the homologous parts. 
The substantive terms applied to the corresponding divisions of the bran- 
chial arches have been modelled on those of the hyoid system; but I have 
deviated in one instance from the rule which has governed throughout my 
nomenclature of the bones, in proposing a second name for a modified homo- 
logue in the air-breathing animals, of a part of the branchial apparatus in 
fishes, viz. that part which is retained even in the human hyoid, and which 
is known in anthropotomy as the ‘ os laterale linguale,’ or ‘ cornu majus ossis 
hyoidei ;’ for this part I have proposed the name ‘thyrohyal,’ for the reasons 
assigned in the note (2) to Table I. 
The names assigned to the bones of the scapular arch (figs. 5, 22, 23, 24, 25, 
* Geol. Trans., vol. v. p. 565. tT Bridgewater Treatise, vol. i. p. 176. 
icaaeiel 
