!t. i ■ . ■ 



i' 



1G2 



REVIEW OF AMERICAN BIRDS. 



[part I. 



tongue, in this instance, is miich longer, and narrower than usual; 

 bifid for more than one-third its length, and fringed at the end, luueh 

 as in Certhiola. It differs from other Sylvk-olidae, also, in having 

 the sides of the tongue, from the middle, folded over and down on 

 the upper surface, though not adherent, nor does the lap extend (|iiiie 

 to the tip. This characteristic of the fold, and the absence of a vor- 

 tical fimbriated lamina adherent to the inner edge of the horizontal 

 bifurcation of the tongue, appears essentially peculiar to this bird. 



This diifcrence of the tongue in "Dendroica tigrina" is so funda- 

 ment-ally great, as compared with all other Sylvicolidee, that were 

 the other characteristics of seasonal changes of plumage, geographi- 

 cal distribution and migration, pattern of coloration, etc. more 

 similar, it would almost warrant our removing it to another family, 

 if not making it the typo of a new one. As it is, it becomes neces- 

 eary to establish a new genus (Perissoglossa) for it, left now among 

 the Sylvicolidfe, but perhaps hereafter to be transferred elsewhere. 



The following diagrams of tongues of some of the Cserebidsi, 

 Sylvicolidae, and Vireonidae have been drawn, at my request, on 

 wood under the microscope by Dr. W. Stirapson ; to whom, also, I 

 am indebted for the accompanying remarks' relative to their charnc- 



' " The tongues are all flsanred, or bifid at the extremity, hy a slit of variabln 

 depth; one-thirl thelengtli of the tongue in Glossiptila, Certhiola, and Periim- 

 glossa, but only one-sixth its length in Vireo; in the others averaging about 

 one-fourth its length. By this slit two forks are formed, which are depressed, 

 corneous, laminiform, and incised along the extremity and outer edge by 

 more or less numerous fissures which form a fringe of flattened setse con- 

 tiguous at base, but becoming narrowed and thus separately projecting in the 

 Bame plane at their extremities. The lateral setae are transverse or even 

 curved backward in Glossiptila, but point obliquely forward in all the other 

 species. 



"The inner edge of the fork is always much thicker than the external 

 laminar expansion, and generally ends in a sharp spine, far stronger than the 

 • proximate setae. But in Glossiptila and Certhiola this inner edge is itself 

 expanded upward into a narrow lamina, which is either in a plane perpen- 

 dicular to the lateral expansion or folded over toward it, and this second 

 lamina is also divided into oblique or longitudinal setae toward its extremity. 

 At the extremity of the fork the two laminae are continent, continuous, and 

 regularly fimbriated around the curve. 



" In Certhiola and Perissoglossa the sides of the tongue at the base of the 

 forks are folded over and inward, but in Certhiola the folds are soldered down 

 to the base and inner edge of the forks ; while in Perisscglossa they are not 

 Boldered, but open outward again anteriorly before the edges become fimbri- 

 ated, so that the extremity of this tonj;ue {Perissoijlossa) is broad, and the 

 setae nearly longitudinal. 



f^.^..' 



