630 mr. a. h. garrod on [ June 1 7, 



femoro-caudal, the accessory femoro-caudal, the semitendinosus, and 

 the accessory semitendinosus) vary ; any one or more than one may 

 be absent in different birds ; and in my dissections my object has 

 always been to record the conditions existing in the specimen under 

 examination. The constancy of the peculiarities in the different in- 

 dividuals of each species, in the species of each genus, and very 

 generally in the genera of each family, makes it evident to any one 

 working at the subject, that much respecting the affinities of the 

 different families of birds is to be learnt from the study of their my- 

 ology, in connexion with the peculiarities of their other soft parts ; 

 and that these features will, in the long run, lead to a more correct 

 classification than one based on the skeleton alone, becomes almost 

 equally certain. 



The variations in the five above-mentioned muscles form the subject 

 of this communication, and the subjoined list contains the results 

 arrived at by myself. A few of the facts now recorded will be 

 found mentioned in the works of Meckel, Sundevall, and others. 

 Reference to them is quite unnecessary, as they can be easily found 

 in the works of those authors. 



The Passeres possess the femoro-caudal, the semitendinosus, and 

 the postacetabular portion of the tensor fasciae ; the accessory semi- 

 tendinosus is present in all except Dicrurus (which has only ten rec- 

 trices) ; the ambiens and the accessory femoro-caudal are absent*. 



The Pici possess the femoro-caudal, the semitendinosus, and the 

 postacetabular portion of the tensor fasciae ; the ambiens and the 

 accessory femoro-caudal are absent, ; and they may be divided into 

 two subfamilies, according to whether the accessory semitendinosus 

 is present or absent. 



The accessory semitendinosus is absent in 



Picus major. Picdides tridactylus. 

 minor. 



The accessory semitendinosus is present in 



Gecinus viridis. Chloronerpes yucatanensis. 



Leuconerpes candidus. Mulleripicus fulvus. 



Melanerpes formicivorus. Hypoxanthus rivolii. 



Yunx torquilla agrees in all these points with Gecinus viridis. 



The SteatornithidcB possess the semitendinosus, and a very narrow 

 accessory semitendinosus. The ambiens, the femoro-caudal, the ac- 

 cessory femoro-caudal, and the postacetabular portion of the tensor 

 fasciae are absent. 



Species examined. 

 Steatomis caripensis. 



The Caprimidgidce possess the femoro-caudal, the semitendinosus, 



* In my paper on the carotid arteries of birds a long list is given of the Pas- 

 seres in which the carotid vessels were examined ; in all these the muscles of the 

 thigh were dissected also. In a specimen of Pomaf.ostotnus temporalis there was an 

 accessory femoro-caudal on the right side; on the left there was not a trace of it. 



