Dr. Otto M. Reis — Structure of Squalordja and ChimcBra. 389 



knorpel" (Hubrecbt), but can only be interpreted as part of the 

 great upper labial cartilage Li of the Selacbians, segmented because 

 tbe lahialis is removed from tbe internasal crest and attached only 

 to tbe labial cartilage (IIa-II&) itself. The first segment is 

 homologous with tbe anterior upper labial Li, while the lower 

 labial cartilage of the Selachian is represented in Chimm-a by Ilia 

 and III6. Hubrecbt describes the latter as binder upper labials, 

 retaining tbe symphysial cartilages of the mandible as lower labials ; 

 but, in the present writer's opinion, tbe latter are homologous with 

 the "submental" cartilages in. Scyllium and Pristiurns,^ and therefore 

 Vetter is right (loc. cit.) in determining Ilia and III6 as lower 

 labials. If one extends transversely the folded lip of ChinKBra 

 (PI. XII, Fig. 7) by raising the skin at the corners of the mouth, 

 the internal aditus of the mouth in these corners is found to curve 

 in the direction of the arrow in Fig. 7. As a consequence the 

 cartilages III lie in the ventral and hinder half of the labial skin- 

 fold, shown in perspective from the anterior or inferior aspect in 

 Fig. 7. Moreover, the attachment of the cartilages III is really on 

 the outer surface of the mandible. The separation of the inner 

 cartilaginous segments II and III is also indicated externally by 

 a little infolding of the skin, which arises from a certain point of 

 the outline of the upper lip and extends to the articulation of H 

 and III. A recurved cartilage 116 extends from the cartilage Ila 

 to this point of the outline (termed by Hubrecht the whole " anterior 

 labial"), to support the great curtain-like lip. On its connection 

 with Ila is to be observed lie in articulation with III. 



In determining the homologies of these parts in Sqiialoraja, it is 

 necessary to remember that we are dealing with a depressed skull 

 instead of one that is laterally compressed. Thus we recognize in 

 the great transverse cartilage Ila the bomologue of the largest 

 cartilage in the labial complex of Chimeera. Further, there may be 

 observed at its distal end the cartilage lie, reflected backwards to 

 the mouth-opening, and possibly the distal support of a similar 

 curtain-like naso-labial fold. With regard to the third cartilage in 

 this region in Sgualoraj'a, we know that it is attached to the hinder 

 side of the two first-mentioned labials, curved in a similar manner 

 and probably situated in nearly the same plane as these. Hence this 

 element can only represent the anterior labial I of Chimara, lying 

 behind the labials II in Sqiialoraja and approaching the mouth- 

 opening on the ventral side, situated behind the labials I and the 

 teeth. The nasal capsules, I suppose, lie between tbe rostral cartilage 

 and the proximal ends of these labials, opening ventrally. 



These cartilages of Sqiialoraja, therefore, cannot be regarded as 

 cirri-like outgrowths of the hinder labials, but represent, in fact, the 

 upper anterior and posterior labials themselves, lying apparently 

 in the interior of a naso-labial fold. Their great development 

 corresponds, indeed, with that of the rostrum and of the rostral spine. 



With reference to tbe spine, A. S. Woodward observes that " we 

 are concerned with an admirable illustration of the principle, that 

 ^ C. Gegenbaur, Untersuch. vergl. Anat. Wirb., pt. iii, p. 206. 



