NERVOUS SYSTEM. VERTEBRATA. 



123 



From the lateral wall of the hemisphere an enormous 

 bulging extends into the ventricle and almost obliterates it. 

 This has been called the epistriatum by Edinger ; its nature 

 is best demonstrated in Sphenodon (fig. 33), in which it is 

 clearly seen to be a large invaginate fold of the pallium 

 (probably the homologue of the pyriform lobe of Mammals). 



This eminence is prolonged further in the caudal direction 

 than the corpus striatum and becomes continuous with a 



Fig. 33. 



HIP. 



NON. HIP. PAU 



CORP. PARATERNI 



EPISTRI." 



SULC. EPISTRI. 



Diagrammatic transverse section through the hemisphere of Sphenodon. 



mass of grey matter, which represents the nucleus amygdalae 

 of Mammals. This nucleus consists of a thickening of the 

 lateral wall of the small descending cornu of the lateral 

 ventricle just behind the caudal extremity of the corpus 

 striatum. On the lateral surface of the brain there is a 

 triangular flattened area corresponding to this body, just as 

 there is on the ventral surface in many mammals (e. g. 

 Erinaceus, Perameles) . 



D.145. The brain of a large Turtle (Clwlone mydas). The dura 

 mater is reflected from the right side, showing its extensive 

 development and the loose trabecular tissue by which the 

 space between it and the pia mater is occupied. A par- 

 ticular development of this tissue consisting of parallel 

 vertical strands occurs above the optic lobes; they give 



