1896.] 



OBMQTIB SEPTA ITT THE PASSEEINE8. 



229 



as I have examined — both Acromyodian and Mesomyodian it should 

 be observed — to the peculiarity which they show in the arrange- 

 ment of the oblique septa. Another distinctive feature of Passerine 

 anatomy is quite desirable. So far as we know at present, there 

 is positively only one character which is absolutely distinctive of 

 Passerine birds. That is, in the condition of the tendon of the 

 patagialis brevis muscle as it was described some years since by 

 the late Prof. Garrod '. Though it is perhaps easy enough to 

 define the Passeres by a combination of characters, none of these 

 characters are everywhere present. It is therefore of more import- 

 ance than in some easily definable groups to add to this single 

 character only wanting in the Pseudoscines (Metiura and Atrichia) 

 another which future research may possibly show to be more 

 universal, and which is at any rate found in several genera widely 

 separated from each other. 



Tig. 3. 



Abdominal and thoracic viscera of Eook displayed by removal of 

 abdominal muscles. 



St., stomach ; L., liver ; O.S., oblique septa. The lobes of the liver are covered 

 by a membrane continuous with the dorsal part of the oblique septa. 



This anatomical feature may therefore have a considerable 



systematic interest. Apart, however, from this, which requires 



still further proof, the conditions which obtain in the Passerine 



bird remind one in soine degree of the Crocodile. The liver-lobes 



1 Coll. Papers, p. 356, 



