136 ALUS. [Vol. XVIII. 



imal articular head of the fourth epibranchial. The posterior 

 portion of the articular head of the latter element, which is us- 

 ually, as already described, found as a separate process with a sepa- 

 rate cartilaginous cap, does not articulate with the cartilaginous 

 strip on the fourth infrapharyngobranchial, but rests upon the 

 dorsal surface of that element posterior to the cartilaginous strip. 



In addition to the two superior and one inferior pharyngeal 

 pads above described, there is, on each side of the head, a small 

 fourth pad, which lies on the lateral surface of the pharynx be- 

 tween the hind ena of the inferior pad and that of the large, pos- 

 terior, superior one. It is furnished with bristles, like the other 

 pads, and consists of a dermal cement component and a small un- 

 derlying, comma-shaped piece of cartilage. The cartilage underlies 

 the anterior end of the piece, and touches, with its enlarged end, 

 and is bound to, the ceratobranchial and epibranchial of the fourth 

 arch at the adjoining articular ends of those two elements. The 

 small end of the cartilage is directed toward the posterior end 

 of the fifth ceratobranchial, but is separated from that element 

 by a considerable interval. It gives insertion to the adductor 

 muscles of the fifth arch. From its association with this muscle 

 it would seem to be the epibranchial of the fifth arch. Its forma- 

 tion of two components, one cartilaginous and the other dermal, 

 the latter furnished with bristles, would, on the contrary seem 

 to indicate that it is an infrapharyngobranchial. What seems to 

 be a corresponding cartilage in Alepocephalus is considered by 

 Gegenbaur (No. 29, p. 24) as a detached process of the fourth 

 arch. A somewhat similar piece in Clupea is considered by the 

 same author as a rare instance of the " Erhaltung der Rudimentes 

 eines zweiten oder obere Gliedstiickes am fiinften Kiemenbogen." 



Between this lateral pharyngeal pad and the inferior and super- 

 ior pads, there are usually three small detached pieces of dermal 

 bone, furished with bristles similar to those on the other larger 

 pads. They all lie approximately superficial to the hind end of 

 the rod-like part of the fifth ceratobranchial. 



The First Suprapharyngobranchial (SPB, I) is a short 

 cylindrical rod of cartilage that runs downward, forward and 

 mesially from the anterior end of the postero-mesial process of 

 the first epibranchial to the small facet on the hind end of the 



