596 : EDWARD PHELPS ALLIS, JR. 
turn, articulates with the dorsal end of the ceratohyal. A mass of 
tough connective tissue that apparently includes the well defined 
hyosuspensorial ligament of Ridewood’s descriptions binds these 
three cartilages together and also strongly attaches the cerato- 
hyal to the hind edge of the suspensorium ventral to the sym- 
plectic process. The biconcave cartilage thus has markedly the 
appearance of a teleostean interhyal. The anterior edge of the 
symplectic process is bound to a slightly developed tubercular 
process of the suspensorium, and on its posterior edge there is a 
small independent cartilage, Ridewood’s interhyal, which is at- 
tached to the postero-internal surface of the hyosuspensorial 
ligament and is also in contact with the biconcave cartilage. On 
the other side of the head of this specimen the hyomandibula is 
without symplectic process, and there is here no biconcave car- 
tilage interposed between the hyomandibula and ceratohyal. 
The tubercular process of the suspensorium is larger than on 
the other side, and the hyosuspensorial ligament is attached 
mainly to it, but partly also to the ventral end of the hyomandi- 
bula. A small cartilage is attached to the hyosuspensorial liga- 
ment in approximately the position of Ridewood’s interhyal, and 
three little bits of cartilage lie along the dorsal and anterior edges 
of the hyomandibula, attached to it by connective tissues. 
The jugular groove is closed externally, throughout nearly its 
entire length, by a tough connective tissue membrane, the vein 
thus being entirely enclosed in the cranial wall. With this vein 
thus enclosed it would seem as if a hyomandibula could readily 
shift upward along the cranial wall from a position ventral to 
the vein to one dorsal to it, but there is no indication whatever 
that any cartilage has so shifted. The epibranchials of the first 
two branchial arches are in contact, by their dorsal ends, with 
the neurocranium ventral to the jugular groove, and are strongly 
bound to it by short longitudinally disposed ligaments that would 
seem to be the dorsal interarcual ligaments. In each of the 
first three arches I find, as van Wijhe did, a small cartilage which 
has strictly the position of a pharyngobranchial. Fiurbringer 
(04) did not find these cartilages, but he found a small carti- 
lage that connected the dorsal ends of the epibranchials of the 
