Macalister — On some Points in Bird Myology, 67 



found it present, and while in Seagulls it is absent, in the Albatross it 

 is present, and it also exists in Sula. 



These are but specimens of the result of the application of myolo- 

 gical varieties for primary taxonomic purposes. 



Muscular characteristics have undoubtedly a very great secondary 

 importance in classification, and as subordinate order and family cha- 

 racters, none are more important ; but they seem to fail utterly when 

 we take them primarily or alone, and try to frame a system by them. 



There are other muscles which may be utilized for these secondary 

 classificatory purposes, as variable among birds. The iliacus, which is 

 absent in the Phasianidae (probably in all the Rasores), but present in 

 Pelargomorphse, Cecomorphae, Aetomorphse, Geranomorphae, &c. A 

 separate gluteus minimus, distinct from gluteus quartus, is a rarely 

 present muscle (Lophophprus). The second vasti are also important 

 bird muscles, and the popliteus, which may be femoro-tibial or fibulo- 

 tibial. The soleus is also variable in its existence, present in Sula 

 Mycteria, Ciconia. The plantaris is a constant muscle, and only varies 

 in the distribution of its extended tendons, which may go to the 

 second, third, or second, third, and fourth toes. The flexor digitorum 

 sublimis is very constant in all birds, with its two perforating ten- 

 dons. The tibialis anticus is also constant, with its two parts, femoral 

 and tibial. The peroueus longus, which is so constant, winding 

 round the outside of the knee, and extending into the perforating 

 flexor of the middle digit, may rarely have no digital extension (Crax) ; 

 Peroneus brevis is variable ; present in the Albatross, Eagle, Phea, 

 Heron ; but absent in the Stork and Pelican. 



Among the forelimb muscles, the infraspinatus is the most variable 

 in its presence, the muscle usually called such being the teres major ; 

 it is small, distinct, and ribbon-like in Lophophorus, Crax, Ithaginis, 

 and Sula ; absent in Tetrapteryx. 



The homologues of the shoulder muscles in birds can only be deter- 

 mined with accuracy by a study of their nervous supply. Those of 

 the hip muscles are little less difficult. 



As Professor Selenka has, in his admirable part of Bronn's Thier- 

 reichs, figured the brachial plexus of a bird, I have endeavoured to 

 do the same for the lumbar and sacral plexus of Tetrapteryx Stan- 

 leyanus in the woodcut on next page. 



R. I. A. rnOC, SER. II., A-OL. TI., SCIENCE. 



