104 Mammalia. Circulatory System. 



Arch of Aorta. 



a. The Human type obtains in 



Bimana ; the higher Caiarrhine Quadrumana ; the Claviculate 

 Rodentia {e.g. Muridse, Castoridae) ; most Finnigrade Sectorialia ; 

 most Bala^nidce^ of the Cete ; most Sirenia ; the Basypodidce and 

 BradypodidcB of the In-Enamellata ; a few broad-chested Marsu- 

 pialia, e.g. Koala and Wombat ; and the Monotrematous Ornithorhyn- 

 cus. 



h. The Bat type obtains in 



the Erinaceidce and Talpidce of the Insectivora ; most Cheiroptera ; 

 and some Delphinidae (not Phocsena) of the Cete. 



c. The Feline type obtains in 



the Strepsirrhine, Platyrrhine, and lower Catarrhine Quadrumana ; 

 most Noyi-claticulate Rodentia ; nearly all Sectorialia (except Pinui- 

 grada) ; the Prohoscidia^'; some Artiodactyla, e.g. the Omnivorous 

 Suidce, and the Ruminants Auchenia^ and Giraffa ; the In-Enamellata 

 JEdentvIa ; and most Marsupialia (exc. see above). 



d. The Ruminant type obtains in 



most Ferissodactyla {e.g. Tapir and Horse) ; and most Ruminant 

 (Bovidae) Artiodactyla. 



Arterial Retia Mirahilia. 



Quadrum.ana. The Limb arteries of the Slow Lemurs (Stenops) 

 exhibit a plexiform arrangement as in the Sloths (Bradypodidae). 



Sectorialia. The Ophthalmic artery (a branch of tho external 

 Carotid) forms in the Cat a vascular plexus in the Orbit. The 

 Brachial artery has a plexiform arrangement in the Walrus. 



Artiodactyla. In the Euminantia a similar orbital plexus is found 

 as in the Cat {supra) : in the Hog and Euminantia ' retia ' are 

 also found in the nasal cavities, formed by the Sphenopalatine artery : 

 again, there is an intracranial * rete ' at the base of the skull in 

 Ruminants ; it is large in grazers (esp. Bovidae), is less in browsers, 

 and least in the Giraffe, which habitually feeds with the head raised. 



CetCi In Phocaena the Intercostal arteries divide into a vast 

 number of branches, forming by their close tortuous interlacement a 

 plexiform mass : from which branches pass into the neural canal, to 

 surround the spinal cord with a similar plexus which increases in 

 thickness near the skuU. Thus the neural axis can receive its 



* Owen. Wagner (p. 45) says that both the Carotids are given off from a 

 single common trunk, situated between the two subclavian arteries ; and quotes 

 it as a very rare arrangement. 



