ABSTRACT Gegenbaur (1872), in his classical work on “Das Kopfskelet der Selachier,” describes (1. c., p. 216), in Raia (species not given) and Raia vomer, two cartilages which he considers to be the homologues of the labial cartilages of Selachii. In Raia (species not given), which is the one first described, one of these two cartilages is shown lying-definitely nearer the anterior end of the ventral surface of the snout than the other cartilage, and, doubtless because of this, the former cartilage is called the anterior upper labial and the other the posterior upper labial. The so-called anterior labial lies, however, farther from the symphysis of the upper jaw and. farther from the upper edge of the mouth than the so-called posterior one, and if the mouth were terminal it would be the posterior instead of the anterior cartilage. Doubtless because of this, Gegenbaur says (l.c., p. 218) that it is evident that the so-called anterior upper labial of the Batoidei corresponds to the posterior upper labial of the Selachii, and the posterior upper labial of the Batoidei to the anterior upper labial of the Selachii. The posterior (oral) edge of the posterior labial is shown (l.c., Pl. 17, fig. 1) in contact, its full length, with the palatoquadrate; its anterior (aboral) edge is said to be bound to the posterior (oral) edge of the anterior labial; and the lateral (absymphysial) end of the latter cartilage is said to be in contact with the palatoquadrate. There is accordingly no space either between the adjoining edges of the two cartilages, or between their posterior (oral) edges and the palatoquadrate, and the nasal groove (Nasenrinne) must accordingly lie either wholly lateral (absymphysial) to both labials or external to them.