ANATOMY OF HETERODONTUS: ENDOSKELETON 459 
From the ventral angle of the mandible a third ligament, the 
ligamentum hyoideo-mandibulare (l.h-m., fig. 6) (the ligamen- 
tum hyoideo-mandibulare externum of Goodey ’10) extends 
posteriorly to be attached to the inner margin of the ceratohyoid 
segment. Near the mandibular attachment this ligament is 
perforated by an artery. 
A most complex suspension is made by a ligament which 
passes from the medial side of the mandible to the ventral side 
of the cranium. For want of a better name I shall call it the 
‘ligamentum complexum’ (I.cp.). Only a part of its course can 
be shown in figures 6 and 7. This arises as a double band (l.cp., 
fig. 7), ventral to the mandibular knob, and passes outward 
over the ceratohyoid to which some of its deeper fibers are 
attached (l.cp., fig. 6); it then gives a bundle of fibers to the 
hyomandibula and, with fibers from the hyoid, runs upward 
and mediad of the hyomandibula to be attached ventrally to 
the base of the cranium slightly anterior to the external carotid 
foramen (see fig. 2). It seems probable that the upper part of 
this ligament at least is comparable to the inferior post-spiracular 
ligament of Ridewood (96). 
It is thus seen that, excepting the suspension rendered by this 
complex ligament just described and by a few fibers from the 
ligamentum hyomandibulo-quadratum, the first arch in the 
posterior region is suspended: entirely by the second. The 
attachment of the first by the second is so complex that it would 
be hard to agree with Huxley (’76, p. 43) that ‘“The ‘epibranchial’ 
(hyomandibula) of the hyoidean arch of Cestracion (Hetero- 
dontus) is just beginning to take on a new function, that of 
suspending the palato-quadrate cartilage and mandible to the 
skull.” 
It may be added that the union of the quadrate and man- 
dibular cartilages is made prineipally by a large ligament, the 
ligamentum quadrato-mandibulare internum (l.q-m.1., fig. 7) 
already mentioned. This attaches to the upper internal border 
of the quadrate above and extends along the posterior border of 
the transverse median ridge of the palato-quadrate (tr.m.r.) 
and over the anterior articulation of the quadrato-mandibular 
JOURNAL OF MORPHOLOGY, VOL. 26, NO. 3 
