Arteries in Monsters of the Dicephalus Group 451 



carotid and the occipital artery. ISTormally the external carotid turns 

 abruptly dorso-laterally beneath the digastric muscle, crosses the caudal 

 extremity of the anterior cornu of the hyoid bone between it and the 

 ventral end of the par-occipital process, whence it turns again dorso- 

 anteriorly and divides into its terminal branches, the internal maxillary 

 and the superficial temporal. 



Near its origin the external carotid gives off the lingual, which crosses 

 the cranial portion of the anterior cornu of the hyoid and passes to the 

 tip of the tongue imbedded in its tissue and gives off many collateral 

 branches. Close to the lingual arises the facial (external maxillary), 

 which at first lies deep beneath the digastric muscle and submaxillary 

 gland, to which it sends small branches. It sometimes gives origin to 

 the sublingual. The facial then emerges from beneath the gland, courses 

 parallel to the jaw for a short distance, turns abruptly, and mounts the 

 side of the face along the anterior margin of the masseter muscle, whence 

 it divides at an obtuse angle into the inferior and superior labials, which 

 supply the muscles of the lower and upper lips respectively. At the 

 ventral extremity of the par-occipital process the external carotid dis- 

 patches a collateral branch, the posterior auricular, to supply the poste- 

 rior region of the external ear and the muscles of the nape of the neck. 

 Immediately anterior to the posterior auricular, the main artery makes 

 a second turn at the angle of the jaw, laterally and anteriorly and 

 bifurcates into its terminal branches, the larger one in the internal max- 

 illary, the smaller, the superficial temporal. The latter vessel gives off 

 the anterior auricular, and sometimes the masseteric. In my specimen 

 of normal pig, the masseteric arose from the anterior auricular. 



A comparison of the above description with Plate V will show that 

 the same distribution is found in the neck and on the outer sides of 

 the componental head of Teras XII, and that variations from this 

 normal condition are confined to the cramped and altered region between 

 the two inner sides of the components. 



If attention is given to component B for a moment, it will be seen that 

 at the point where the left common carotid gives off the left external 

 carotid, the main artery is apparently continued anteriorly and medi- 

 ally by curving slightly across the anterior cornu of the hyoid to a posi- 

 tion along the median axis of the body, whence it continues forward and 

 passes between the two componental snouts, winding through the S-shaped 

 passage between the overlapping rami and emerging upon the inner 

 lateral and dorsal sides of the face. Opposite the cranial extremity of 



