SKELETON 



83 



forward by a large plate (mesethmoid?) lying dorsal to the mouth, this part being 

 roofed by two 'dorsal cartilages,' the anterior articulating with the annular 

 cartilage supporting the mouth. A subocular bar extends forward from each 



- Fig. 82. — Ventral and lateral views of the skull of lamprey {Petromyzon marinus), 

 rter Parker, ad, anterior dorsal cartilage, bb, branchial basket; gc, gill cleft; Ic, labial 

 cartilage; Idm, lateral distal mandibular; Ig, lingual cartilage; nc, nasal capsule; oc, otic 

 capsule; on, optic nerve; pc, pericardial cartilage; pd, posterior dorsal cartilage. 



otic region and an elongate lingual cartilage extends from the mouth back to the 

 gill region. Several other elements occur, the names and positions of which 

 may be seen from the figures. 



Fig. 83. — Side view of cranium of Bdellosloma, after Ayers and Jackson, b, basal 

 plate; br, branchial basket; c, cornual cartilage; d, dental plate; h, hyoid; /, lateral labial 

 cartilage; n, nasal tube; nc, notochord; 0, otic capwule; oc, olfactory capsule; pq, subocu- 

 lar bar; sp, suprapharyngeal plate. 



The myxinoid skull (fig. 83), the development of which is unknown, is 

 readily interpreted so far as basilar plate, trabeculae and otic capsules are con- 

 cerned. The large nasal capsule is continued forward by a latticed framework 



