•i4 PARIETAL SEGMENT, OR VERTEBRA. 



(common to this and the next arch in advance); the lower 

 one " stylohyal," No. 38. The hoemapophysis is a broader, 

 slightly arched bone; the upper division is called "epi- 

 hyal," No. 39; the lower division, "ceratohyal," No. 40. 

 The h^mal spine is subdivided into four stumpy bones, 

 called collectively "basihyal," No. 41; and which, in most 

 fishes, support a bone directed forwards, entering the sub- 

 stance of the tongue, called "glossohyal," No. 42; and 

 another bone directed backwards, called "urohyal," No. 43. 



The ceratohyal part of the hsemapophysis supports, in 

 the cod, seven long and slender bent bones, called " bran- 

 chiostegal rays," 44. The number of these rays difiers 

 greatly in different fishes; the protopterus has but one 

 ray, the blenny has two rays, the carp three rays — a very 

 common number is seven ; but the chps has thirty bran- 

 chiostegal rays. They are of great length in the angler- 

 fish (lophius), in which they serve to support a membrane, 

 developed to form a large receptacle on each side of the 

 head of this singular fish. Into these receptacles the 

 small fishes are transferred, which the angler attracts 

 within reach of its mouth, by the movable rod, line, and 

 bait attached to the top of its enormous head. In ordi- 

 nary fishes, the branchiostegal rays support a membrane 

 which helps to close the gill-slit, and by its movements 

 contributes to the direction of the branchial currents. It 

 is an appendage, or rudimental limb, answering to the 

 pectoral fin diverging from the h^mal arch, in the ad- 

 joining occipital segment. 



The penultimate segment of the skull above described 

 is called the "parietal vertebra;" and the haemal arch is 

 called the "hyoidean arch," in reference to its supporting 

 and subserving the movements of the tongue. 



The next segment, or the second of the skull, counting 



