THE MANDIBULAR AND HYOID MUSCLES OE MAMMALS. (521 
inserted into and arising from the stylo-hyale (fig. 42) . A sta- 
pedius of usual origin and insertion is present. 
Mackintosh described the posterior digastric'of CKolo^pps as 
arisingfrom the stylo-hyale^but did not mention the existence 
of any muscle arising from the mastoid and inserted into the 
bar. Such a muscle^ however, is pictured in a hgure of 
Schulman under the title of mastoideo-hyoideus. 
d^oldt stated that the posterior digastric was absent in 
Tamandua, but described and pictured a stylo-hyoideus/^ 
innervated by the N. facialis, taking origin from the os tym- 
panicLim and inserted into the cranial end of the hyoid cornu, 
and also described a portion of the intermandibularis as 
arising from the hyoid cornu. These two muscles are in all 
probability the dorsal and ventral portions of the posterior 
digastric. Tliis identification is rendered all the more certain 
by his statement that there is an anastomosis between the 
mylohyoid branch of the fifth aud the seventh nerves. 
Owen described three muscles in My rni ecophaga juba ta 
— a stylohyoideus passing from the petro-hyoid to the 
stylo-hyale, a cerato-hyoideus passing from the cerato- 
hyale to a commissural tendon with a slip to the sterno- 
mandibularis muscle, aud a ‘^constrictor salivaris’^ passing 
from the cerato-hyale downwards over the salivary reservoir to 
the commissural tendon and blending* with the back of the 
intermandibularis. It is probable from his description and 
figures that his “ stylo-hyoideus ’’ aud “ cerato-hyoideus are 
the dorsal and ventral portions of a divided posterior digas- 
tric. Leche stated that the constrictor salivaris is innervated 
by the N. my lo - hyoideus and is to be regarded as a differ- 
entiated part of the intermandibularis. 
The condition of the hyoid ventral constrictor is thus 
variable in Edentates, even in closely related species. Thus it 
is undivided in Brady pus tri dactyl us, divided into upper 
and lower parts in Bradypus marmoratus; undivided in 
Dasypus villosus, divided in Dasypus novemcincta. 
And in at least one Alarsupial — Cuscus maculatus — the 
condition is variable within the same species (vide p. 619). 
