816 



cells, is not. conspicnous in this specimen altliougli tlie tliicUened 

 fibre zone lateral to the external rnednllary lamina (Fig. VI) is com- 

 parable to the area figured by Edingkk, Wallenberg and Holmes 

 (op. cit) in Lothrix lateus (Taf. Hi, {\^. 5 &nA &) SinA Sylvia hortensis 

 (Taf. IV fig. 6). 



In the sections under examination the hyperstriatnm shows no 

 clear sign of snbdivision. In most birds the lamina mednllaris 

 hyperstriati divides the hyperstrialnm into the hyperstriatum superius 

 and hyperstriaiuin inferius of Ariëns Kappers (1922). As this author 

 rightly points out (op. cit. note I, p. 23) Parker's figures, in the 

 woi'k already mentioned on the development of tlie brain of the 

 kiwi, show only two intraventricular primordia which probably 

 lepresent the palaeostriatum and hyperstriatum inferius, the hyper- 

 striatum superius being apparently absent, (Parker 1891, Plate 19, 

 Fig. 304). This point however needs re-investigation upon material 

 in a better state of preservation than tiiat at present available. 



Frontally the hyperstriatum covers the frontal pole of the meso- 

 striatum and forms the frontal extremity of the cerebral hemisphere 

 [caput hyperstriati, Fig. IV). 



The caudal part of the corpus striatum receives the fronlo- 

 epistriatic tracts (Fig. XIV). This region constitutes the secondary 

 epislriatum or archistriatum (Ariëns Kappers 1908). It is the area 

 called epistriatiim in the memoir of Edinger, Wallenberg and Holmes. 

 The fissura stvio-archistriatica is not visible in the bird's brain. The 

 archistriatum is connected to its fellow of the opposite side by a 

 great strand of fibres {coiiiDiissiira interepi.striatica, Edinger). This 

 bundle forms the main constituent of the comuiissura anterior (vide 

 Fig. X) which is large and conspicuous in this brain (Fig. IX — X). 

 Some of these fibres accompany the fronto-epistriatic tracts; the 

 majority form a distinct fibre field in the ventral part of the meso- 

 striatum (Fig. IX— XIII). 



c. The signifieance of the blood vessels accompanying the 

 lamina medullaris externa. 



In his recent work on the morphology of the corpus striatum, 

 Elliot Smith (19196) has emphasised his contention that the great 

 ventricular eminence which forms such a conspicuous feature of the 

 cerebral hemisphere of Sphenodon is pallial in origin. He has intro- 

 duced the term hypopallium to designate this structure because "it 

 is pallial in origin ; it lies below the main portion of the pallium 

 • which forms the roof of the hemisphere; and morphologically and 



