184 REPORT—1846. 
23, 50-52) and its appendages (tb. 53~ss) agree so closely with those which 
they have always borne as to require no explanation here. The chief 
surprise of the anthropotomist will be occasioned by their being included 
amongst the bones of the head. That the upper or pectoral extremity 
and its supporting arch form actually integrant parts of the occipital seg- 
ment of the skull, will be proved in the memoir on the general homologies 
of the bones of the head. I may, here, however, in reference to the terms 
‘ulna’ and ‘radius,’ request the anatomist to compare the skeletons of the 
perch or cod with that of the porpoise. The pectoral extremity is in the 
form of a fin, and in both fish and marine mammal it is applied, in a state of 
rest, prone to the side of the trunk; in this position it will be seen in the 
Delphinus, that the radius is downward, and the ulna with its projecting 
olecranon upwards. I take this as the guide to the homology of the two bones 
that support the carpal series of the pectoral fin in fishes. Cuvier, however, 
gives the name of ‘cubital,’ perhaps on account of its angular olecranoid 
prolongation, to the lower bone, and ‘radial* to the upper bone: and in 
these determinations he is followed by M. Agassiz. Both bones coalesce 
with the supporting arch in the lophius and some other fishes; and since, in 
the lophius, two of the carpal bones are unusually elongated, Geoffroy mistook 
these for homologues of the radius and ulna. The condition of the pelvic 
member or ventral fin is, in fact, here repeated in the pectoral; there being 
no homologous segment of thigh or leg interposed in any ventrals between 
the supporting (pelvic) arch and the fin-rays representing the tarso-me- 
tatarse and phalanges. The earlier stages in the development of all loco- 
motive extremities are permanently retained or represented in the paired fins 
of fishes. First the essential part of the member, the hand or foot, appears : 
then the fore-arm or leg; both much shortened, flattened and expanded, as 
in all fins and all embryonic rudiments of limbs: finally comes the humeral 
and femoral segments; but this stage I have not found attained in any fish. 
It is with considerable doubt that I place, qualified by a note of interroga- 
tion, Cuvier’s “troisiéme os qui porte la nagoire pectorale” as the homologue 
or rudimental representative of a ‘humerus.’ Normally, I believe this proxi- 
mal member of the radiated appendage of the scapular arch not to be di- 
stinctly eliminated from that arch in the class of fishes. The Siluroids are 
examples of a similar confluence of the first segment (preoperculum) of the 
diverging appendage of the tympanic arch with that arch. With regard to 
the lower, distal or apical element of the scapulo-coracoid arch, always the 
largest bone of the arch in fishes, Cuvier’s idea that it is the ‘ humerus,’ far 
less accords with the law of the development, the connections, and the essen- 
tial nature of that bone, than the more prevalent view, that it represents the 
clavicle: a view entertained by Spix, Meckel, and Agassiz, by Wagner, 
who calls it ‘ vordere Schliisselbein,’ and by Geoffroy, who calls it ‘ furculaire.’ 
I have, however, been induced to regard the lower element of the scapular 
arch, in fishes (fig. 5, 52), as homologous with that bone, the ‘ coracoid,’ which 
progressively acquires a more constant and larger development in descending 
from mammals to fishes, and which is manifestly a more essential part of the 
arch than the clavicle, since it is more constant in its existence, and always 
more completely developed in birds and reptiles; and especially since it con- 
tributes more or less of the surface of attachment for the radiated appendage, 
which the clavicle never does. With reference, also, to the Cuvierian deter- 
mination of the hzemapophysial portion of the occipital inverted arch in fishes, 
this is unquestionably as essential an element of the arch as is the ‘ coracoide’ 
in other vertebrates ; and it is the most important part in the piscine class, in 
no member of which does it present the slightest approach to the character of 
