I860.] Cerebral System of the Class Mammalia, 185 



feet clavicles ; pectoral mammae ; vesicular and prostatic glands ; a 

 discoid, sometimes double, placenta. The Quadrumana have a well- 

 marked threefold geographical as well as structural division. 



The Strepsirhines are those with curved or twisted terminal nos- 



Q Q 2 2 



trils, with much modified incisors, premolars 5 — r or — - in number, 



and molars with sharp tubercles : the second digit of the hind limb has 

 a claw. This group includes the Galagos, Pottos, Loris, Aye- Ayes, 

 Indris, and the true Lemurs ; the three latter genera being restricted 

 to Madagascar, whence the group diverges in one direction to the con- 

 tinent of Africa, in the other to the Indian Archipelago. 



The speaker exhibited drawings by Joseph "Wolf, of an Aye- Aye, 

 {Cheiromys Madagascariensis) which had been recently transmitted, 

 well preserved in spirits, to the British Museum. He pointed out, by 

 comparison of its brain with that of a similarly sized Rodent, its 

 combination of a type of cerebral organ truly gyrencephalous ia the 

 proportions of the hemispheres, and in the pattern of the few convolu- 

 tions, with a dentition so similar to that of a Rodent as to have deceived 

 Gmelin and Cuvier in regard to its ordinal position in the mammalian 

 class. The equally remarkable modification of the hands was pointed 

 out, concurring with the dentition in enabling the Aye- Aye to extract 

 its favourite food, the larvae of Coleoptera, burrowing in hard wood, 

 from their hiding-places. 



The Platyrhine Quadrumana are those with the nostrils subter- 



g 3 



minal and wide apart ; premolars ^ — 5- in number, the molars, with 



o — o 



blunt tubercles ; the thumbs of the fore-hands not opposable or want- 

 ting ; the tail in most prehensile ; they are peculiar to South America. 

 The Catarhine Quadrumana have the nostrils oblique and approxi- 

 mated below, and opening above and behind the muzzle : the pre- 



2 2 



molars are ;- — - in number ; the thumb of the fore-hand is opposable. 



They are restricted to the Old World, and, save a single species on 

 the rock of Gibraltar, to Africa and Asia. The highest organized 

 family of Catarhines is tailless, and offers in the Orang, Chimpanzee, 

 and Gorilla, the nearest approach to the human type. 



Climate rigidly limits the range of the Quadrumana latitudinally : 

 creational and geographical causes limit their range in longitude. 

 Distinct genera represent each other in the same latitudes of the New 

 and Old Worlds ; and also, in a great degree, in Africa and Asia. 



The fourth and highest type of the Mammalian brain rises at once, 

 and without transitional rudiments of the hippocampus minor, hinder 

 horn of lateral ventricle, or concomitant lobe of cerebrum protruding 

 backward beyond the cerebellum, to that marvellous structure which 

 is peculiar to our own species. The sole representative of the Arcuen- 

 CEPHALA,* is the genus Hmno. His structural modifications, more 



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OLpyoj^ to over-i-ule ; iyKi({>0(,\Ofy brain. 



