150 von Ihering, The De?idrocolaplidce. LApril 



It follows therefore, as already suggested by Fiirbringer (p. 1419), 

 that the supposed difference between pseudoschizorhinal and holo- 

 rhinal skulls in the Dendrocolaptidse does not exist in fact, but 

 that they are modifications of little importance which serve only 

 in a limited degree in the characterization of genera, and not at all 

 in the differentiation of families. 



Most families which are related to the Dendrocolaptidse have 

 the skull holorhinal. We find in them, however, similar modifica- 

 tions to those existing in the Dendrocolaptidse. For example in 

 the Formicariidse some species of Myrmotherula and Drymophila 

 show prolongation of the narrow posterior portion of the nasal 

 foramen almost up to the intermaxillary and it is probable that 

 further studies based upon richer material will demonstrate that 

 among the Formicariidoe too there are species with pseudoschizo- 

 rhinal as well as holorhinal skulls. Of greater importance however 

 is the modification in the bony nostril of the Formicariidse. In 

 Batata cinerea (Plate XII, figs. 3^4) it is closed for nearly its entire 

 length (14 mm.) by a thin vertical osseous membrane, the anterior 

 portion of which is perforated by a nostril 4 mm. in diameter, while 

 the posterior part contains a second nostril communicating with the 

 buccal cavity. I have found the same structure in Thamuophilus 

 and Conopophaga lineata, the aspect of the several skulls being 

 quite different but the structure essentially the same, except for 

 the fact that the membrane of the nasal cavity remains soft in 

 some and becomes ossified in others. 



This style of skull structure in which instead of one large bony 

 nostril we have two, a posterior and anterior one, I propose to call 

 amphirhinal. 



In the Dendrocolaptidse, therefore, while the type of structure is 

 always the same and there are no essential anatomical differences, 

 the dimensions and proportions of the different bones and foramina 

 vary to a degree rarely found in one family. The enormous varia- 

 tion in the form of the beak is seen in such genera as Xenops, 

 Synnallaxis, Philydor and Campylorhamphus. In connection with 

 the differences in form we find variation in the condition of the 

 nostrils which are in some genera holorhinal, in others pseudo- 

 schizorhinal. The base of the beak is also differentiated variously, 

 sometimes provided with an intermaxillary frontal fontanelle, 

 sometimes not; while between the two parietal bones in some 



