252 MR. A. H. GARROD ON THE [May 5, 



IV. The presence or absence of the ambiens muscle in the genera of 



the Columbae. 

 This muscle, of which the slender tendon runs in such a peculiar 

 manner obliquely across the knee, arising from the supero-anterior 

 margin of the acetabulum, and inserted into the muscular fibres of 

 the flexor perforatus of the toes, is found in the greater number of 

 the Pigeons I have examined, being present in about three fourths 

 of the genera. 



The ambiens muscle is present in 



Calcenas, Lopholcemus, 



Carpophaga, Macropygia, 



Chalcopelia, Metriopelia, 



Chalcophaps, Ocyphaps, 



Chamcepelia, Phaps, 



Columba, Pterocles, 



Didunculus, Turtur, 



Ectopistes, Tympanistria, 



Leptoptila, Zenaida, 



Leucosarcia, Zenaidura. 



The ambiens muscle is absent in 



Geopelia, Ptilonopus, 



Goura, Starnoenas, 



Phlogcenas, Treron. 



The combination of the above-collected facts ought to be of con- 

 siderable service in any attempts at classification ; for, leaving the 

 number of rectrices out of the question for the minute, of the eight 

 possible variations of the three remaining characters, there are seven 

 which are found to exist ; in other words there are Pigeons known — 



(1) With an oil-gland, caeca, and an ambiens muscle, viz. Columba, 

 Ectopistes, Macropygia, Pterocles, and Turtur. 



(2) With an oil-gland, no caeca, and an ambiens muscle, viz. Ca- 

 lcenas, Carpophaga, Chalcopelia, Chalcophaps, Chamcepelia, Lepto- 

 ptila, Leucosarcia, Lopholcemus, Metriopelia, Ocyphaps, Phaps, 

 Tympanistria, Zenaida, and Zenaidura. 



(3) With no oil-gland, no caeca, and an ambiens muscle, viz. Di- 

 dunculus. 



(4) With an oil-gland, caeca, and no ambiens muscle, viz. Phlo- 

 gcenas. 



(5) With no oil-gland, caeca, and no ambiens muscle, viz. Star- 

 noenas. 



(6) With an oil-gland, no caeca, and no ambiens muscle, viz. Geo- 

 pelia, Ptilonopus. 



(7) With no oil-gland, no caeca, and no ambiens muscle, viz. Tre- 

 ron, Goura. 



The only combination not found being that (8) in which, of the 

 three structures concerned, the oil-gland only is wanting. 



The relative value of these different structural peculiarities is the 

 point on which their value in classification evidently hinges. The 

 number of rectrices being the most variable of them, its importance 



