51 
the remainder of the bone being separated from the underlying 
cartilage by the temporal hole of SAGEMEHL, that hole lodging an 
anterior extension of the dorsal muscles of the trunk. Along the 
under surface of the lateral edge of the bone two short lamellae are 
said to project downward and somewhat mesially, and to firmly embrace 
the sharpened, dorso-lateral edge of the chondrocranium. One of the 
two lamellae lies along the lateral surface of the skull, extending 
downward approximately to the dorsal edge of the articular facet for 
the hyomandibular. The other lies along the lateral edge of the floor 
of the temporal hole. These lamellae, although closely applied to the 
surface of the cartilage they embrace, are said by SAGEMEHL (No. 28, 
p. 59) to be everywhere separated from it by a layer of perichondrium. 
The entire bone is, accordingly, considered by him as of purely dermal 
origin. 
In Teleosts, SAGEMEHL says (No. 29, p. 507) that the squamosal 
consists of two parts, one of them being of dermal origin while the 
other presents all the characteristics of a primary ossification. In the 
Characinidae the dermal part of the bone is said by him (No. 28, 
p. 59) to be a bony plate that lies in the same level as the other 
dermal bones that cover the top of the skull. Along its lateral edge 
it is said to be connected with the primary portion, which is described 
as a bony plate directed medianly and forming a part of the floor 
and lateral boundary of the temporal hole and a part of the lateral 
surface of the skull. The dermal part of the bone is traversed by 
the main infraorbital lateral canal, and lies dorsal to the muscles that 
fill the temporal hole. The primary part of the bone lies lateral or 
ventral to those muscles, and is traversed by the external semicircular 
canal of the ear. It, extends downward along the lateral surface of 
the skull beyond the dorsal articular end of the hyomandibular, and 
the posterior part of the articular facet for that bone lies on its 
external surface, and, according to the figures, is lined with cartilage. 
The median wall of the temporal hole is said to be partly of cartilage 
and partly of membrane, a fascia closing a large round opening which 
is always found leading through the cartilage, from the hole, directly 
into the labyrinth recess of the cranial cavity (No, 28, p. 81.) 
In the Cyprinidae the mesial edge of the dorsal, dermal part of 
the squamosal is said by SAGEmEHL (No. 29, p. 550) not to reach 
the exoccipitale, as it does in all the Characinidae, a certain space, 
covered by the parietal, being left between the two bones. In certain 
of the Cyprinidae this space is said to be so greatly enlarged that 
the temporal hole becomes in part uncovered; and in still others the 
4* 
