1«88.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 173 



NOTES ON THE OSTEOLOGY OF THE THRUSHES, MIMING, AND 



WRENS. 



BY FREDERIC A. LUCAS. 



(With Plate xxxvn.) 



The present paper was commenced more than a year ago, but many 

 circumstances have combiued to prevent its completion sooner. It was 

 undertaken at the suggestion of Mr. Robert liidgway, in the hope of 

 throwing a little light on the relations of the Mimince. This peculiarly 

 American subfamily, formerly placed among the Thrushes, has of late 

 found a resting-place with the Wrens, and in the A. O. U. Check List 

 stands at the foot of the family Troglodytidce, Galeoscoptes standing last 

 of all. I must at the outset confess that it has been a somewhat diffi- 

 cult matter to select for comparative purposes characters that should be 

 at once well marked and of undeniable taxouomic value. Judgiug from 

 an examination of many specimens such characters would seem to be 

 found in the shape of the maxiilo-palatines, pars plaua, costal process, and 

 coracoid. Many bones which might be supposed to offer good points 

 are found untrustworthy when put to the test. 



Looking down upon two parallel series of Crania, one of Thrushes 

 and one of Wrens, the first will be found to differ from the second in the 

 much greater breadth of the lachrymal region due to the lateral ex- 

 pansion of the pars plana. 



Viewed in the same way the skulls of the Mimince are seen to be in- 

 termediate between the two, although the Mimince vary somewhat 

 among themselves; Harporhynchm, due allowance being made for its 

 size, having as narrow a skull as the Wrens, while Galeoscoptes and 

 Melanoptila approach, but do not equal, the Thrushes. 



Another very obvious character for comparative purposes is found in 

 the relative width of the external process of the nasal and the angle sub- 

 tended by this bone and the pars plana. In all the Thrushes examined 

 the external process of the nasal is broad, in all the Wrens and in the 

 Mimince it is narrow. In the Thrushes the angle formed by the nasal 

 and pars plana is very acute, while in the Wrens and Mocking-Thrushes 

 the corresponding angle is more or less open, most so in the Wrens. In 

 these particulars Galeoscoptes comes nearer the Thrushes than do its 

 associates. 



Aside from the small taxonomic value of the lachrymal it is a most un- 

 satisfactory bone to deal with, not only from its small size but from its 

 delicate texture and the insensible manner in which it merges into the 

 surrounding membrane. This causes the lachrymal to be frequently 

 lost in the preparation of a skull, in spite ot the most watchful care, and 



