NECTURUS MACULATUS 403 
(b.) Brain case. 
1. Frontal. 
2. Parietal. 
8. Parabasal. 
(c.) Upper jaw. 
1. Maxillary arch. 
a. Premaxillary. 
2. Palatopterygoid arch. 
a. Vomer. 
b. Palatopterygoid. 
Tur ViIsckRAL SKELETON. 
(a.) General morphology of the arches. 
(b.) Mandible. 
1. Dentale. 
2. Angulare. 
3. Spleniale. 
(c.) Hyobranchial apparatus. 
(d.) Suspensorial relations of the hyoid. 
Tur FREE SENSE CaAPsULEs. 
(a.) Nasal capsule. 
(b.) Optic capsule. 
Tue TEETH. 
ComMPARISON OF NOMENCLATURE. 
General Description of the Skull and its Parts. 
The term “skull” is used here in its most restricted sense and does not include either 
the mandible, the hyobranchial apparatus or the nasal and optic capsules. These elements 
are for the most part easily detachable from the firmly consolidated skull, and are thus, in 
the anatomical sense, not to be included with it. A single exception may be made in the 
case of the nasal capsule with regard to which the usage of authors differs, since, although 
anatomically distinct in Necturus, it belongs genetically to the primordial skull. Wieders- 
heim, for example, who is correct from the morphological standpoint, figures it in his 
drawing of the skull, while both W. K. Parker (in Proteus) and Huxley fail even to find 
it. In this paper it will be omitted from consideration at present to receive special treat- 
ment later on. 
The skull, then, denuded of all its extraneous elements, will present an appearance 
much as is given in figures 2 and 3 (plate 63). The general outline suggested a pentagon 
to Huxley, but in order to see it as such, one should imagine the ligaments restored that 
