284 REPORT— 1846. 
chelonians, the ichthyic independence of the parapophyses (4, a)... In batra- 
chians the epencephalic arch is reduced to the two important elements, the 
reurapophyses ; which meet and join each other below as well as above the 
foramen magnum, and develope the exogenous zygapophyses, or two occipital 
condyles, for articulation with the corresponding processes of the neural arch 
of the atlas. The basioccipital, if it exists in batrachians, is rudimental and 
confluent with the basisphenoid, and the supraoccipital is in like manner 
recognisable only as the posterior border of the hackwardly produced parietal. 
The parapophyses are short exogenous processes of the neurapophyses of this 
much simplified epencephalic arch in all batrachian reptiles. 
‘The chief modification that distinguishes the above-described segment of 
the crocodile’s skull from its homologue in the fish, is the absence of an 
attached inverted or hemal arch. We recognise, indeed, the special homo- 
logues of the piscine constituents of that arch in 50, 51 and 52, fig. 22. The 
upper suprascapular piece (50) is however free, disconnected from any seg- 
ment, and retains, in connection with the loss of its proximal or cranial 
articulations, its cartilaginous state : the scapula (51) is ossified, as is likewise 
the coracoid (52), the lower end of which is separated from its fellow by the 
interposition of a median, symmetrical, partially ossified piece called ‘epister- 
num’ (As). The power of recognising the special homologies of 50, 51, and 
52 in the crocodile, with the similarly numbered constituents of the arch H1 
in fishes (fig. 5), though masked not only by modifications of form and pro- 
portion but even of very substance, as in the case of 50, depends upon the 
circumstance of these bones constituting the same essential element of the 
archetypal skeleton: for although in the present instance there is superadded 
to the adaptive modifications above cited the rarer one of altered connections, 
Cuvier does not hesitate to give the same names (suprascapulaire) to 50 
and (scapulaire) to 51, in both fish and crocodile: but he did not perceive or 
admit that the narrower relations of special homology were a result of, and 
necessarily included in, the wider law of general homology. According to 
the view of this law here taken, we discern in 50 and 51, fig. 22, a teleologically 
compound pleurapophysis, in 52 a hemapophysis, and in hs the hemal 
spine, completing the hemal arch. 
The general relations of the scapulo-coracoid arch to a hemal or costal 
one have been long recognised, but the vertebral segment to which it apper- 
tains seems not hitherto to have been suspected, and has certainly not been 
satisfactorily determined. Oken, who had observed the free cervical ribs in 
a specimen of the Lacerta apoda, Pallas (Pseudopus), deemed them repre- 
sentatives of the scapula, and this bone to be, in other animals, the coalesced 
homologues of the cervical pleurapophyses*. In no animal are the conditions 
for testing this question so favourable and obvious as in the crocodile: not 
only do cervical ribs coexist with the scapulo-coracoid arch, but they are of 
unusual length and are developed from the atlas as well as from each suc- 
ceeding cervical vertebra: we can also trace them beyond the thorax to the 
sacrum, and throughout a great part of the caudal region, as the sutures of 
the apparently long transverse processes of the coccygeal vertebrae demon- 
strate in the young animal; the lumbar pleurapophyses being manifested 
at the same period as cartilaginous appendages to the ends of the long dia- 
pophyses. 
* “ Auch die Scapula nicht ein Knochen, sondern wenigstens eine aus finf Halsrippen 
zusammengeflossene Platte ist.”—Programm, &c., 4to, 1807, p. 16. He reproduces the 
same idea of the general homology of the scapula in the ‘ Lehrbuch der Natur-philosophie,’ 
1843, p. 331, § 2381. Carus also regards the scapulo-coracoid arch as the reunion of seve- 
ral (at least three) protovertebral arches of the trunk-segments. ‘ Urtheilen des Knochen 
nnd Schalen gerustes, fol. px. 
