58 ILLINOIS BIOLOGICAL MONOGRAPHS [58 



COMPARISON OF THE NASAL CAPSULES IN THE ANURA 



The division of the Anura into the suborders Aglossa and Phaneroglossa 

 is borne out by this study of the nasal capsules; for Pipa would appear to 

 be far removed from the other Anura, and because of the large vacuities 

 in the chondrocranium it may be said to be more like the Urodeles. 



In all of the Anura, the extension of the pterygoid process to the nasal 

 capsule is the normal condition, and recalls this relationship in Crypto- 

 branchus Furthermore, the planum tectale, apparently a lateral growth 

 from the. columna ethmoidalis, unites to the pterygoid, the two forming 

 in Bufo the lamina externa, which forms the side wall of the capsule; while 

 in the adult Rana, the anterior connection of the lamina externa is lost, the 

 united pterygoid and tectale forming the anterior maxillary process. 



The cavum cranii of Pipa is not as well developed as in other Anura, 

 the alisphenoids being but little higher than the planum basale, and less 

 crest-like in their appearance. The forebrain in Pipa lies dorsal to the 

 posterior part of the nasal sac, rather than posterior to it as in Bufo; and, 

 if the olfactory nerve may be regarded as sufficient evidence for the deter- 

 mination of homologies, then that part of the basale in Pipa, anterior to 

 the foramen olfactorius, must be the perpendicular ethmoidal wall in Bufo 

 and other Phaneroglossa. This change in the relative position of these 

 parts may be explained by the statement of Gaupp that the chondrocrania 

 of larvae of Rana fusca suffer a reduction in the sagittal plane during 

 metamorphosis. 



In both groups, the roof of the capsule, anterior to the region just 

 described is formed by a fusion in the middle line of the ethmoidal columns, 

 which also unite to the planum verticale. In Bufo, the extent of the tectale 

 lateral to the verticale is considerably more than in Pipa, where the medial 

 parts of each nasal sac are but slightly covered and suggest for Pipa a more 

 complete fusion of the ethmoidal columns. There is no floor of the nasal 

 capsule in Pipa, while in all the Phaneroglossa the planum basale extends 

 forward from the cavum cranii to the tip of the capsule, where each lateral 

 angle expands into the alinasal cartilage. The presence of these alinasals 

 in Pipa would suggest that the ventral half of the planum verticale must be 

 a fused and greatly reduced trabecular plate, homologous to the anterior 

 planum basale in the Phaneroglossa. 



The lateral wing of the capsule, the so-called ethmo-palatine of Parker 

 or planum terminale of Gaupp, but more properly designated the lamina 

 externa in Bufo, is formed, partly from the pterygoid and partly from the 

 columna ethmoidalis. In both groups two cartilage bars unite the lamina 



