MANDIBULAR ARTERY — AORTIC ARCH 103 



but also in certain of the Batoidei, and Raffaele ('92, p. 46) says 

 that it aborts and completely disappears in the Torpedinidae. 

 Raffaele further says that the posterior efferent arteries of the 

 branchial arches develop, in Torpedo, before the anterior ones, 

 this order of origin thus accounting for the presence of a posterior 

 artery and the absence of an anterior one in the hyal arch of the 

 embryos examined both by himself and by Dohrn. In the 

 branchial arches, both of the Selachii and the Batoidei, the ante- 

 rior efferent artery is said by Dohrn later to become the larger 

 and more important one, and, in the Holocephali and Teleostei, 

 Parker ('86) says that this anterior efferent artery alone is found 

 in the adult. 



In embryos of Mustelus, probably somewhat older than the 

 embryos studied by either Dohrn or Raffaele, Wright ('85) found 

 no afferent mandibular artery arising either from the truncus 

 arteriosus or the ventral end of the afferent artery of the hyal arch, 

 but he did find an artery, apparently not described by Dohrn, 

 that had its origin from the ventral end of the anterior efferent 

 artery of the first branchial arch. This artery is said by Wright 

 first to send a branch to the thyreoid gland and then to run 



upwards and outwards on the ventral surface of the hyoid arch, 

 supplying the parts between it and the mandible, till it reaches the 

 hyomandibulo-hyoid articulation, and probably anastomoses there with 

 the afferent artery of the mandibular pseudobranch. From its course 

 I conclude that this artery is the thyro-mandibular artery of Dohrn; 

 if so, its newly acquired origin from an efferent vessel of the first bran- 

 chial arch is worthy of note. We shall find that it corresponds entirely 

 in its course to a vessel which originates in the same way in Lepidosteus, 

 and which is obviously the art. hyoidea or hyo-opercularis of the 

 Teleostei. 



Later in the same work Wright says of this artery in Lepi- 

 dosteus : 



As remarked above, its course agrees with that of the thyro-man- 

 dibular artery of Dohrn. It appears to me to be homodyiiamous with 

 the nutritive or branchial arteries which spring from the succeeding 

 efferent arteries, . . . The Selachians also possess similar nutri- 

 tive vessels, and it is easy to understand why that of the hyoid arch 

 should be larger than those of the succeeding arches, whereas it is diffi- 



