250 THE MESODERMAL DERIVATIVES 



=^Basibranchial (copula) — single cartilage between ceratohyals. 

 *Hypobranchials — paired, posterior to ceratohyals, and derived from third 



visceral arches. Articulates also with basibranchial. 

 *Ceratobranchials — three or possibly four slender processes within third to 



sixth visceral arches, extending from hypobranchial on each side. 

 *May be ectodermal. 



