122 ALLEN 



unites with the hyoidean artery to form the mandibular artery, 

 but in this genus the hyoidean artery branches in the region of 

 the preopercle. The ventral fork passes through a foramen in 

 front of the preopercle to become the mandibular artery ; while 

 the dorsal fork passes along the inner surface of the hyomandib- 

 ular and anastomoses with the pseudobranchial artery. Usu- 

 ally the pseudobranchiaU artery has its origin from the main 

 stem of the external carotid (facialis-mandibularis) in the facial 

 region, but with Anoplo^o7na the pseudobranchial artery rises 

 from the external carotid close to its origin from the first effer- 

 ent branchial artery ; in fact it might be said to rise with the 

 external carotid from the first efferent branchial artery, being 

 fully as large as the carotid. An ophthalmic or efferent pseudo- 

 branchial artery always rises from the efferent pseudobranchial 

 arteries, which supplies only the choroid coat of the eye. In 

 Ofhiodon the ventral artery rises from the ventral union of the 

 second and third pairs of efferent branchial arteries ; while in 

 the other genera it comes from the union of the second efferent 

 vessels. This artery in Anoplo^onia is a short vessel barely 

 reaching the pelvic bones ; the suppl}?- for the ventral fin region 

 comes from the subclavian. In all the genera but Anoplofoma^ 

 the pharynx artery, from which the coronary rises, has its 

 source directly from one of the second or third efferent bran- 

 chial arteries, but in this genus it rises from the ventral artery. 

 There is always a distinct circulus cephalicus formed by the 

 union of the encephalic, internal carotid, common carotid, first 

 efferent branchial, and the first epibranchial arteries. Both 

 pairs of epibranchials terminate in a common chamber from 

 which the dorsal aorta, coeliaco-mesenteric, and subclavians 

 have their origin ; in some cases, however, this chamber is 

 simply an opening between the aorta and the coeliaco-mesen- 

 teric. The dorsal aorta is essentially the same in all the gen- 

 era ; passing caudad beneath the vertebral column it gives off 

 the renal and spermatic arteries to the kidney and the reproduc- 

 tive organs, the neural, hremal, and intercostal arteries to the 

 body wall, and finally terminates in the caudal lin. The sub- 

 clavian arteries are practically the same in all the forms studied ; 

 they may arise from a single trunk or separately as was de- 



