51] THE NASAL ORGAN IN AMPHIBIA H1GGINS 51 



evident that the planum verticale is a reduced internasal plate, and that the 

 so-called ventral process is a modified cornu. In the early stage, according 

 to Parker, this cornu trabeculae is free from the tectale, ending near its 

 median margin in a blunt process; but in the stage that I have studied the 

 two are united, thus recalling the relation of these parts in the Urodeles. 

 The dorsal process is evidently something additional in Pipa and cannot 

 be compared to any Urodelan structure; although it exists in some form or 

 other in all Anura, where it has been called the oblique cartilage because of 

 its relation to the nasal organ. This cartilage may be a part of the original 

 internasal plate of Parker's stage, the intermediate part between it and 

 the verticale having been resorbed, leaving the elongate gap upon the dor- 

 sal surface of the capsule. 



The capsule of Pipa is unlike any other Amphibian, differing markedly 

 from any Urodele or Phaneroglossa, although similar in many ways to the 

 other aglossal genus Dactylethra. The chondrocranium of Parker's 

 younger larva is more complete and lacks the large gaps of the later stage, 

 in which the resorptive processes have so greatly changed the appearance 

 of the capsule. The planum tectale is evidently a growth from both the 

 columna ethmoidalis and the trabecula, and has subsequently become 

 united posteriorly to the pterygoid process, while anteriorly it has grown 

 forward into the triangular process which has erroneously been called the 

 ethmopalatine cartilage. 



From the above identification of the ethmoidal column, it would 

 appear that the planum verticale has developed by a fusion, in the middle 

 line of the skull, of the trabeculae and the columnae ethmoidales; the 

 ventral part of the verticale being trabecular in origin, the dorsal half 

 derived from the united columnae ethmoidales. In this relationship, then, 

 we have a condition very largely Amblystomal; for in the 34 mm. larva, 

 the ethmoidal columns unite to the coalesced trabeculae to form the thick 

 planum verticale so characteristic of Amblystoma, but which in Pipa is so 

 greatly reduced in width. 



BUFO AMERICANA 



The nasal capsule of the Phaneroglossa is far more complex than that 

 of the Aglossa, and the olfactory organs which lie entirely anterior to the 

 forebrain are better protected by cartilage structures. 



In a larva of Bufo vulgaris, one-third of an inch long (Parker, 1876), 

 the trabeculae have fused to form an internasal plate, smaller than in Pipa, 

 from which they diverge forward forming the cornua trabeculorum with 

 an internasal space between them. So that this early stage of Bufo is 

 similar to my 28 mm. Rana viridescens, yet to be described. 



In my single stage of Bufo americana, whose body length is 9 mm., a 

 complex nasal capsule has been chondrified; and resembles in many ways 



