608 EDWARD PHELPS ALLIS, JR. 
cartilaginous arches were undoubtedly in a measure held and 
fixed at a certain distance from each other, while at the middle 
of their lengths, where the dorsal and ventral halves articulated 
with each other, a certain freedom of motion existed. Further- 
more, while it is the dorsal portion of the cleft that longest per- 
sists in fishes, it is said to be the ventral portion of the cleft that 
persists the longer in the Amphibia. But even if the cleft were 
not actually closed here first, it is here that the branchial rays 
first differentiate in ontogeny (Dohrn), and here that they are 
the most strongly developed. It is accordingly natural to sup- 
pose that, as the cleft aborted, whether this began at the middle 
of its length or at its ventral end, a time would come when these 
middle rays of the mandibular series, or their protons (Anlagen), 
developing in the tissyes which bridged the space between the 
mandibular and hyal arches, would come into contact, by their 
distal ends, with the hyal cartilages. These rays, or their pro- 
tons, would then give rise, not only to the symplectic cartilage 
of the Teleostei, but also to the several and varying ligaments 
that here connect the mandibular and hyal arches in the Selachii, 
excepting probably the large ligamentum mandibulo-hyoideum, 
which is said by Edgeworth (’11, p. 212) to have been derived 
from the muscles of the region. In the Batoidei the only one of 
these several ligaments that is shown by either Parker or Gadow 
is, as already stated, a stout one extending from the ventral end 
a the quadrate to the ventral end of the hyomandibula, which is 
exactly the position of the symplectic cartilage in the Teleostei. 
The other ligaments here found in the Selachii have perhaps not 
been developed in the Batoidei because, in these fishes, the space 
separating the mandibular and hyal arches was too wide to be 
bridged by the tissues that represented the primitive rays, these 
tissues then here aborting or being dispersed. 
The symplectic of the Teleostei is said by Stohr (82) to be 
developed as a primarily independent element which lies close 
against the hinder edge of the quadrate and later fuses with a 
ventral process of the hyomandibula; which is strictly in accord 
with its being a branchial ray related to the mandibular arch. 
It lies, in the adult, internal to the arteria hyoidea (afferent man- 
