M 



outward prolongation of the maxillary below ; iu capsule, the sclerotic, U cartilaginous. The 

 uajttl rapsnlea are also cartilaginous, with vertical tliu elated by membrane ; they are situated 

 a* each ride and below the naial plate. 



Pretexted by Prof. Oven, F.R.S. 



Order X. HOLOCEPHALI. 



The pelvis with the pelvic or ventral fins and claspcrs of a male Chimera. 



The short narrow processes which extend above the place of articulation of the ventral fins 

 are like rudiinental iliac bones: the expanded portion* which meet below repmrnt the 

 ischb-pubic bones : they are each of them perforated by a large round aperture filled by 

 membrane and resembling the obturator foramen. The claiper* or sexual holders air long, 

 ubcylindhcal and hollow, communicating in the recent fish with a glandular blind sac open- 

 ing into the base of the clasper. The cartilage, answering to the tibia, supports the rays of 

 the ventral fin and the clasper. 



Ilunteriait. 



888. Part of the dried cartilaginous skull of the Southern Chinurra (Callorhynrkut 

 AtutraKt). 



The left upper jaw and teeth have been vertically bisected ; each upper jaw has one small 

 anterior dental plate and a large posterior one, of an inequilateral triangular form, with a 

 sinuous crushing surface. The upper surface of each of these teeth is concave from side to 

 side, to that it encases the alveolar border of the upper jaw, in a manner analogous to the 

 broad teeth of the Cut radon. Both the anterior and posterior dental plates in the upper 

 jaw meet at the median line of the mouth. The two dental plate* of the lower jaw are of a 

 subtriaagular form, with tin- posterior and external rides gently curved ; the broad grinding 

 surface is convex on the inner and concave on the outer ride ; a trenchant margin divides 

 this from the lateral surfaces of the dental plate. In the longitudinal vertical section of these 

 teeth their coarse tubular structure is evident to the naked eye. There is a large pulp-cavity 

 at the posterior parts of both the upper and lower dental plate*, and, when the pulp is re- 

 moved, the exposed surface of the base of the tooth presents a reticulate character from the 

 Urge are* of the medullary tubes into which the processes of the pulp are continued. These 

 tube* radiate towards the grinding surface of the tooth, and dichotomize as they proceed. As 

 these tubes advance towards the surface their cavity becomes gradually obliterated by calca- 

 reous salts, deposited in concentric layers and perforated even-where by minute calcigerous 

 tubes ; thus the substance of the tooth increases in density as it approaches the triturating 



surface. 



Hunttna*. 



