218 B. NATURAL HISTORY. 
tal; ExO, Exoccipital; SO, Supraoccipital; OpO, Opisthotic; Pro, 
Prootic; EpO, Epiotic; Fr, Frontal; PoF, Postfrontal ; Prf, Prefron- 
frontal; N, Nasal; Pmx, 
Premaxillary ; Mx, Max- 
illary; Ecp, Ectoptery- 
goid; Q, Quadrate; Art, 
Articular; Cor, Coro- 
noid; D, Dentary; V, 
Foramen ovale.) The 
= obtuse extremities of 
Fig. 17. — Xenopeltis unicolor (Siam). the opisthotic and ex- 
occipital support together the os quadratum. 
In the rather more specialized Kenopeltis, the opisthotic is no 
longer intercalated between the prodtic and exoccipital, but lies 
over the common suture of the two, united by a squamosal suture. 
This important change transfers us from the Tortricina to the 
Asinea, as defined by Miiller. (See fig. 17, OpO.) Throughout 
. the latter suborder it only increases in length, which prolongation 
reaches its highest expression in the venomous serpents of the. 
suborder Solenoglypha. It has been homologized with the squa- 
mosal in these groups by Huxley (Elements of Comparative Anat- 
omy), but incorrectly, as I believe, and attempt to show in 
considering that bone. 
Among the Batrachia this element is not distinct, except in 
Necturus. (See fig. 22, posterior view of cranium of Rana mu- 
giens.) I have failed to find it entirely distinct in larve of various 
ages of Amblystoma, Spelerpes, and Gyrinophilus; for though a 
suture from the fenestra ovale to the foramen condyloideum sepa- 
which I say in the definition of the Scolecophidia, p. 230, “no prefrontal.” 
This should have read “no opisthotic.” The prefrontal is largely developed in 
Typhlops, while the maxillary is much reduced, and concealed on the inferior 
face of the cranium alongside the vomers. In the portion devoted to the 
Lacertilia, p. 225, several expressions occur which need explanation, owing to 
the fact that the homologies of some of the elements were not at that time 
worked out. Thus the “temporal bone” is the prodtic, and the “mastoid” is 
the opisthotic. I must also correct the nomenclature of the elements of the 
mandible here, and in Clidastes, as published in Trans. Amer. Philos. Soc., 1870, 
pp. 214-16. Angular should read articular, articular should read surangular, and 
subarticular should read angular. Incut 51, figs. 3 and 5 belong to one bone, which 
is the angular. 
