VISCERAL ARCHES OE THE GNATHOSTOME FISHES. 303 
The Homologies of the Muscles related to the 
Visceral Arches of the Gnathostome Fishes. 
By 
Edward Phelps Allis, jr., 
Menton, France. 
Witli Plates 21 and 22 and 1 Text-figure. 
In 1874 Vetter published his well-known work on the 
muscles related to the visceral arches of the Selachii, and, 
clothed somewhat with Gegenbaur’s authority, it immediately 
became the recognised standard of reference, and all later 
work relating to the subject has apparently been greatly 
influenced by it. Certain parts of Vetter’s descriptions have, 
however, always been to me obscure, but I have attributed 
it to my not being personally familiar with the anatomy of 
the Selachii. Considering that this familiarity had been in 
a measure acquired by my present work on the cranial 
anatomy of Chlamydoselachus, I recently carefully re-read 
Vetter’s descriptions, but I still found the particular parts 
referred to neither precise nor clear. Tiesing’s (1895), Ruge’s 
(1897), and Marion’s (1905) later works not helping to a 
proper comprehension, I then had recourse to dissections of 
such few specimens of the Selachii, other than Chlamydo- 
selachus, as I had at my disposal. The result has been to 
lead me to consider the particular parts referred to,, in the 
several works above mentioned, incorrect, and it has also 
unexpectedly led me to seriously question every one of the 
several instances cited by Edgeworth (1911) in which one of 
■these visceral-arch muscles of fishes is said to be innervated, 
