EEPORT ON THE SPHENISCID.E. 221 



of the gland is continuous. It passes backwards to open on the surface of the cutaneous 

 papilla, as above described. 



In certain species of Penguin, but not in all, a distinct muscular slip, derived from 

 the levator coccygis muscle, passes backwards, to be inserted into the base of each 

 half of the coccygeal gland. This slip I have observed in Eudfptes chrysolophus, 

 Spheniscus magellanicus, and Pi/gosceles tceniatus. The function of this slip, when 

 present, is by no means apparent, as it can hardly act as a compressor of the gland. 



Except in size, the coccygeal gland of different species presents no deviations from 

 that above described in Eudyptes chrysocome. 



Tliyroid Gland. 



The thyroid gland (PI. XL fig. 1) in every species of Penguin occupies the position 

 common to all birds. In Eudypte-'^ chrysocome it is rather smaller than a garden pea, 

 and lies in contact with the inner side of the common carotid artery, half an inch from 

 the origin of that vessel. In Pygosceles and in Spheniscus demersus it is situated 1 inch 

 from the point of bifurcation of the innominate artery. 



In every species of Penguin, with the exception of Aptenodytes longirostris, in which 

 it consists of two distinct lobes, this gland resembles that of Eudyptes chrysocome. 



On the Subdivision of the Spheniscid^. 



A reference to the foregoing description of the anatomy of the Penguins at once con- 

 vinces us that these birds together fonn a natural group, every member of which is 

 possessed of certain anatomical peculiarities which serve at once to associate it with its 

 fellows, and to separate it from the members of other groujas which more or less closely 

 resemble the Sj^heniscidse. To collect together the various distinctive features of 

 the different anatomical systems of the Penguins, and to contrast them with those of 

 other birds would be to repeat the summaries which are placed at the end of each of the 

 foregoing sections, and is therefore unnecessary. Suffice it here to direct attention to 

 the very remarkable uniformity of anatomical detail which prevails in respect of the 

 muscular, nervous, blood- vascular, and urino-genital systems of every species of Penguin. 

 It is true that, with regard to these systems, individual peculiarities manifest themselves 

 in different species, but these are unimportant and of but little value in attempting to 

 arrive at a natural subdivision of the group into genera and species. When, however, we 

 proceed to the consideration of the osseous, digestive, and respiratory organs of these 

 birds, we find that the individual peculiarities are so pronounced that, taking them into 

 consideration, we experience no difficulty in associating together a greater or lesser 

 number of species to form genera, every member of each of which agrees with its 



