CHONDROCRANIUM OF EUMECES 135 
side of the ‘radix dorsi sellae’ figured by Voit (’09 b, fig. 6) in 
the rabbit is perhaps even more closely homologous with the 
reptilian foramen. The further course of the nerve in this fig- 
ure, between the rudiments (‘Restknorpel’) of the primary cranial 
wall, emphasizes still further the general homology of mammal 
and reptile as regards the relations of the sixth cranial nerve. 
4, OCCIPITAL REGION 
The general form of the occipital region (fig. 6) is essentially 
as in Lacerta—an approximately pentagonal frame around the 
foramen magnum (f.mag.). The base of the pentagon consists 
of the posterior part of the basal plate, already described. 
From each of its posterolateral angles there arises a somewhat 
flattened occipital arch or pila occipitalis (oc.), which extends 
upward and outward (laterad) to the dorsolateral angle of the 
pentagon. Here the arch broadens suddenly and unites with 
the otic capsule along the median surface of the prominence of 
the posterior semicircular canal (prom.s-c.p.), thus dorsally 
closing the fissura metotica (fis.m-ot.). The expanded arch, still 
fused with the otic capsule, then extends dorsad and mesad into 
the scanty tectum posterius (tect.p.), which forms the apex of 
the pentagon. The tectum posterius is the only cartilaginous 
roof of the skull posterior to the nasal capsule. From the middle 
of the tectum a very long processus ascendens (pr.asc.) extends 
upward and forward, as in Lacerta, furnishing protection to the 
endolymph sacs. The pentagon of the foramen magnum is 
less regular in Eumeces than in Lacerta; its dorsolateral sides 
are complicated by thin projections of cartilage into the opening, 
and the ventral side is interrupted by the more conspicuous 
condylar projections and intercondylar notch of the basal plate. 
In Lacerta the fissura metotica is carried much further dor- 
sally than in Eumeces, although the upper extension is reduced 
to minimum width and contains no important organs; the ex- 
treme is seen in Emys (Kunkel, ’12 b), where the occipital arches 
remain entirely free from the otic capsules. Complete dorsal 
fusion from a.little below the dorsolateral angle of the foramen 
JOURNAL OF MORPHOLOGY, VOL. 34, NO. 1 
