18S7.] 



ANATOMY OF CERTAIN AUKS. 



45 



the bodies of both of them. I will at once observe, however, 

 that the form of the heart is quite ditlerent in these two birds, being 

 not only smaller in S. antiquus than it is in the Marbled Auk or 

 Murrelet, but apparently longer, and decidedly more pointed in the 

 former than it is in the latter, wherein it is a thicker organ with a 

 bluntly rounded apex (tig. 2). 



Fiff. 1. 



Fig. 2. 



Fig. 1. Anterior aspect of the lower larynx, heart, and viscera of SynthlihorTiam- 

 phus antiquus. /, fat overlying in front of the lower larynx ; s.t, 

 sterno-trachealis muscle of the left side ; h, heart ; I, right lobe of 

 liver ; /', left lobe of liver ; g, gizzard. 



Fig. 2. Same parts and aspect of the corresponding organs in Brachyrhamphus 

 marmoratiis ; lettering the same as in fig. 1, with t.I, the left tracheo- 

 lateralis muscle. 



The figures are drawn life-size by the author, and are from the specimens of 

 the Murrelets lent by the Smithsonian Institution. 



Extraordinary differences are to be observed in the livers of these 

 two Murrelets, both as regards form and size. In each the left lube 

 is rather the larger, and descends somewhat further into the 

 abdomen. But in S. antiquus the hepatic lobes are considerably 



