BY WILLIAM A. HASWELL, M.A., B.SC. 83 



CARCHARODON RONDELETII. 

 Plate I., Figs. 1-1. 

 Skull and Visceral Arches. 



The upper surface_of the occipital region of the skull (Plate 



1. fig. 1) is horizontally directed, and is continuous without in- 

 terruption with the upper surface of the periotic and ethmoidal 

 regions. The occipital crest is not well marked behind, but in front 

 forms an elevated, though rounded, ridge, ending between the 

 auditory foramina in a nearly vertical border. The parietal groove 

 is shallow and open, and is excavated on the hinder part of a promi- 

 nent parieto-frontal crest, which reaches as far forwards as the 

 frontal foramen. A small median foramen lies in its front portion. 

 On either side of the parietal groove, running forwards and slightly 

 outwards, is a rounded elevation, which stops short a little way in 

 front of the auditory foramen, and behind does not quite reach to 

 the posterior margin of the skull. The anterior and posterior 

 portions of this correspond to the elevations of the anterior and 

 posterior semi-circular canals respectively. The vestibular promi 

 nence is not well marked. 



The articular surface for the hyo-mandibular (Plate I., fig. 



2, At.), is borne outwards and backwards from the cranium 

 on a very prominent process, which is produced into thi-ee 

 prominent angles, one directed backwards, a second upwards, 

 backwards, and a little outwards, and a third, the shortest, 

 forwards and outwards. The posterior portion of the process 

 projects far behind the plane of the foramen magnum, and 

 bears a large aperture for the glosso-pharyngeal on its upper 

 and posterior surface at some distance from the posterior angle j 

 but behind the plane of the foramen magnum and of the 

 orifice of the vagus ; below it reaches to the plane of the base of 

 the skull ; and the anterior and upper portion reaches as high 

 as the middle of the foramen magnum. The articular surface 

 itself consists of two portions — a hinder, much larger, which is a 

 shallow concavity and is boundei below by a slight raised ridge ; 



