CHONDROCRANIUM OF EUMECES 129 
Gaupp (’00) also notes that in Chelone midas the notochord 
enters the basal plate ventrally, in marked contrast to the dorsal 
position in Lacerta and Tropidonotus. Finally, in Emys (Kun- 
kel, 711, 712 b) and Crocodilus (Shiino, ’14) the notochord is de- 
scribed as wholly embedded in the basal plate, although Kunkel 
believes it to have lain on the dorsal surface in earlier stages of 
Emys. This variability in the reptiles finds its parallel in am- 
phibians and mammals. Thus, according to Gaupp (’05 b), in 
Triton taeniatus the notochord lies dorsal and in Siredon ventral, 
while in Triton cristatus it is embedded in the basal plate. Gaupp 
(08 a), Tourneux (12), and de Burlet (13 a, ’16) have collated 
the data for the Mammalia, showing an extreme dorsal position 
in Echidna and Mus, a fully ventral position in Bradypus, com- 
plete investment in Bos and Phocaena, and a variety of combi- 
nations of these types, sometimes very complex, in other forms. 
The contrasts between closely related species as well as between 
different ontogenetic stages of the same animal indicate the 
correctness of Gaupp’s view (08a) that little significance 
attaches to the position of the notochord. 
3. Nerve foramina of basal plate 
The basal plate is intimately associated with the points of 
exit of two pairs of cranial nerves—XII, hypoglossus; VI, 
abducens. The foramen for the facialis and the fissura metotica, 
with its complex of nerves and blood-vessels, can be more con- 
veniently discussed in connection with the otic region. 
Nerve XII. The hypoglossus foramina (figs. 2, 3, 6, 7, and 8, 
f.n.XII.) are located essentially as in Lacerta, near the lateral 
edge of the basal plate, the posterior foramen lying just opposite 
the union of the basal plate with the occipital arch; but the 
number is only two on each side in stage 5. Other stages of 
Eumeces show variability in this number. Thus in stages 2 and 
4 there are two foramina on one side and three on the other (in 
stage 4 the third foramen is very minute), while stage 6 shows 
three foramina on each side, as in Lacerta. 
