430 Bulletin American Museum of Natural History. [Vol. XXVII, 



Infraorbital foramen. Nerve Vv. Constant in Theria (? Cetacea). 

 Foreshadowed in the Cynodont sknll ( ?). Must have been originally dorsal 

 to the maxillary. ? Prototheria. 



Ethmoid foramen, for the eniri) of the nasal nerve (a branch of VJ and 

 ethmoid artery. ?Constant in Theria. 



Interned orbited {spJtenopedatine) foramen. Xerve V^. Constant in 

 Theria. Always pierces or notches the vertical plate of the palatine. 

 ?Prototheria. 



Anterior pededine foramina. Xerve V,. Constant (?Cetacea). 



Posterior pcdeitine foramina. Nerve V^ (and blood vessels). Variable 

 in position, often piercing the palatine, sometimes represented by vacuities 

 (Marsupialia, certain Insectivores). 



Interned auditor t/ meaiu.'t (in petrosal). Nerves VII, VIII. Constant. 

 The facial nerve (VII) ])asses through the ])etrosal and leaves the skull by 

 the stylomastoid foramen. 



Stylomastoid foramen (VII). Constant. "Lies between the tympanic 

 bulla, the paroccipital process and the mastoid portion of the periotic" 

 (Reynold's, /. c, p. 400; cf. supra, \). 224). 



Foramen laccrum poster i us. X'erves IX, X, XI. Constant? 



Cond(/lar foramen. Nerve XII. Sometimes d(Kible (e. g., Marsupials, 

 Ursus, Tapirus, Lepus) or even tri])le (Arefomijs, p. 820). Absent (confluent 

 with for. lac. post.) in Arsinoitherium, Prol)oscidea. 



II. Foramina for blood vessels. 



'llie location of the foramina for the two main branches of the carotid 

 artery is of great importance. 



Alisphenoiel canal. For the external carotid. Posterior opening in 

 front of foramen ovale; tunnels or grooves alisphenoid and, running forwards, 

 sometimes becomes confluent with the foramen rotundum {e. g., Canis) but 

 sometimes opens separately (Rodents). Absent in Monotremes, INIarsupials, 

 usually present in Insectivores, Creodonts (sometimes absent, p. 306) ; afford- 

 ing family distinctions in the Fissi]:)e(lia; present in Condylarthra, Ambly- 

 poda, Hyracoidea, Arsinoitheria, Proboscidea, Perissodactyla; absent in 

 Artiodactyla. 



Foram£n lacerum medium (Flower, = foramen lac(>rum anterius Weber). 

 In the Doo- the internal carotid runs forward through an entocarotid canal 

 lying between the tympanic bulla, the petrosal and the basisphenoid, and 

 enters the cranium through the foramen lacerum medium. In the Poly- 

 protodonts (Figs. 1, IG) a similar canal (probably for the posterior branch of 

 the entocarotid) pierces the basioccipital. In Ccenole.^tes (Fig. 15) this 

 canal runs forward to the "carotid foramen" of the basisphenoid (see below). 



