720 INDIVIDUAL VARIATION IN EQUUS ASINUS. 
Smaller tarsal bones very frequently united by ankylosis into 
a single mass, without any external indication of disease. This 
is the condition known to veterinary surgeons as “ occult spavin/'’ 
We are not yet prepared to attribute to it any morphological 
importance. 
Cuneiforme parvum composed of one or of two portions. 
Splanchnoskeleton . 
Ossification or calcification of the posterior portion of the 
sclerotic occurs in aid asses. 
Os hyoides presents between cerato- and stylo-hyal on each 
side a bony nodule representing the epihyals, which are well 
developed in the ox. 
An os cordis has been observed in the ass; it is always present 
in the ox. 
Myology. 
Head .—We generally observe muscular fibres which run from 
the antero-external angle of orbicularis palpebrans beneath 
zygomaticus to the outer surface of buccinator. These represent 
laclirymolabialis of the ox, and are seldom seen in the horse. 
They are deficient in some asses. 
Retractor labii superioris sometimes has a supplementary 
portion which runs from the common point of origin of the 
muscle to the tendon of the nasalis longus labii superioris, which 
it draws downwards, and also to spread out by some of its fibres 
over the superior part of the “ false nostril.” 
The “ false nostril,” the peculiar nasal pouch of Equidse, 
undergoes considerable variation at its extremity, sometimes 
presenting a slight tendency to bifidity of its Gul-de-sac. In the 
ass it is seldom used; for the animals are never driven to such 
extremes of rapid progression as the horse. Hence we often 
find these sacs distended with masses of laminse of epithelial 
debris. The dilatatores naris vary in their arrangement in rela¬ 
tion to this pouch; thus, ordinarily a continuous series of fibres 
extends to it from above, behind, and below, being the superior 
and inferior dilators. But we have seen excessive development 
of the band against the cul-de-sac of the pouch and deficiency of 
the other parts of the series. The posterior extremity of 
retractor labii superioris has sometimes a muscular addendum 
connecting it with the zygomatic ridge. 
Mylohyoideus varies somewhat in being divided generally at 
its anterior part into two distinct planes. 
GenioJiyoideus sometimes sends a small distinct band to 
genioghssus at about the centre of the intermaxillary space. 
Ilyopharyngeus , in addition to its usual attachment to the 
