35] THE NASAL ORGAN IN AMPHIBIA— HIGGINS 35 



THE NASAL CAPSULE OF THE GYMNOPHIONA 



EPICRIUM GLUTINOSUM 



Considerable diversity of opinion has existed in the past in regard to 

 the systematic position of the Caecilians. Cope (1889) classed them as a 

 family of the Urodeles, related to them through Amphiuma; while the 

 cousins Sarasin (1890), following Cope, also regarded them as Urodeles, 

 considering Amphiuma a neotenic Caecilian. Kingsley (1902) reviewed 

 the evidence as to the position of the group, showing that many points 

 supposed to indicate relationships, were based upon erroneous statements 

 or misconceptions and that the Gymnophiona are to be regarded as a 

 distinct group, without any close relations to any other existing Amphibia. 



To determine to what extent, if any, the nasal capsules of this group 

 would shed light upon their relationships to the Urodeles, two larvae of 

 Epicrium glutinosum were studied, in which chondrification was well 

 advanced and the nasal capsules completely formed. 



Peter (1898) has described the chondrocranium of a young Caecilian; 

 and Winslow (1898) a stage in which the embryo is still spirally coiled 

 within the egg, considerably younger than my earlier material. In con- 

 trast to all other Amphibia, the trabeculae of each side are double (Fig. 

 32), consisting of a dorsal and ventral bar in the position of trabecular 

 crest and trabecula, the dorsal doubtless being the homologue of what 

 Sewertzofif (1897) has called the alisphenoid cartilage of the Elasmobranchs. 

 On either side of the eye, the dorsal and ventral trabeculae are united by a 

 postorbital and preorbital band, the optic nerve passing through the 

 large gap between them. Anterior to the preorbital band, the lower or 

 true trabecula inclines toward the median line, and is united with its mate 

 by a slightly convex planum basale {ph), which lacks the trabecular 

 thickenings of the plana of Urodeles. The posterior and lateral margins 

 of the planum are straight, the latter more anteriorly curving outward 

 where it passes into the posterior margin of the cornu trabeculae, which 

 forms the floor of the capsule; while anterior to the cornu the planum 

 narrows considerably and is continuous in front into a pair of small proc- 

 esses, the tips of the trabeculae, separated from each other by a wide 

 internasal space. 



The planum verticale {pv) is a narrow plate of cartilage, arising from 

 the anterior half of the median line of the basale and extending dorsally 



