366 



Vertehrata. 



is the large dentigeroue dent ale, which meets its fellow of the other side 

 anteriorly. The upper portion of the hyoid, which is united with the 

 coiTesponding part of the mandibular arch, is represented by two bones; a 

 large one, the hyomandibular, articulated with the skull, and a smaller, 

 lower ossification, the symplectic. For the membrane bones connected with 

 the hyoid, see below, under the gUl apparatus. 



In the Dipnoi, the upper portions of the mandibular and hyoid arches ai-e 

 ooncrescent, and partly ossified, thus possessing so far, the same relations as in 

 the Teleostei ; the arcade thus formed is, however, connected immovably with 

 the skull. 



In tlie Ganoids and Teleosteans, two membrane bones 

 arise anteriorly on eitber side of tbe bead, quite independent of tbe 

 visceral arcbes : an intermaxilla or premaxilla, and a, 

 maxilla, whicb is sometimes represented by several bones, and 

 is situated bebind, or bebind and witbin, tbe former; tbe premaxillse 

 are connected in tbe midline, and witb tbe maxillae, are usually 

 somewbat loosely connected to tbe anterior end of tbe skull, forming 

 tbe upper margin of tbe moutb, wbilst tbe bones lying upon tbe 

 mandibular cartilage form tbe lower edge. 



Tbe sboulder girdle is, in tbe Selacbians, an unpaired 

 cartilaginous arcb, sometimes divided into two pieces, wbicb lies bebind 



Fig. 303. Shoulder girdle and fore limb of 

 brane bones (6 clavicle), e, / the actual shoulder girdle (« 

 h fin rays. 



a. P e r c h . a', a", b, c, mem- 

 soapnla, / coracoid), g radialia, 



tbe gill bars, and reacbes up on to tbe side of tbe bead. In tbe 

 Ganoids and Teleosteans it is divided into two balves, one on 

 eitber side of tbe body, and closely united to eacb part is a series of 

 membrane bones, of wbicb tbe largest is a long, flattened, somewbat 



