1890.] The Hemologies of the Fins of Fishes. 411 
A later contribution to this branch of the subject is contained 
in a paper entitled “ Notes on the Fins of Elasmobranchs, with 
considerations on the Nature and Homologues of Vertebrate 
Limbs,” by St. George Mivart, published in the Transactions of 
the Zoological Society of London, February, 1879. After noting 
and discussing the opinions of Oken, Carus, Cuvier, Owen, Geg- 
enbaur, Balfour, Parker, and others, upon this and other questions 
relating to the history of vertebrate appendages, the author states 
his conviction “that the nature of the paired and azygos limbs is 
fundamentally the same.” This conviction was formed through 
finding various degrees of coalescence between the cartilaginous 
rays supporting the dorsal fins, and various degrees of connection 
or continuity between such fin-supports and the axial skeleton. 
Scylium canicula, Ginglymostoma cirratum, and still more Noti- 
danus cinereus, are examples of this. In the latter, the rays are sup- 
ported by one continuous basal cartilage. Pristis and Pristio- 
phorus show continuity between the dorsal fin-cartilages and the 
skeleton, and this may aid in the support of the saw-like rostrum. 
In Notidanus, Chiloscyllium, and Raia, there is much resemblance 
between the skeleton of the ventral and dorsal, in Notidanus, be- 
tween the ventral and anal, while the ventrals of Polyodon are 
simple parallel rays like the simplest form of the dorsal skeleton. 
If the ventrals are thus admitted to be of the same nature with 
the vertical fins, the pectorals must also be of the same nature. 
Prof. Mivart endorses the idea of Mr. Thacher with regard to 
the origin of the limb-girdles, viz.: that they are lateral ingrowths 
from the skeleton of the paired fins. The objection to this con- 
clusion that has been drawn from the attachment of the pectorals 
by a shoulder-girdle instead of by direct longitudinal adhesion 
are met by the considerations that such adhesion would impede 
the flexure of the body in swimming, that the pectorals are too 
low to abut directly on the vertebral column, and that such con- 
nection is prevented by the intermediation of the body-cavity. 
The entire theory is thus summarized by Mivart: 
1. Two continuous lateral longitudinal folds were developed 
similar to a dorsal and a ventral fold. 
2. Separate, narrow, solid supports, with their long axes di- 
