Barrows.] 150 [April 4, 



Dr. H. P. Bowditch gave an account of his investigations 

 on the growth of children. 



Prof. E. S. Morse exhibited a series of mud-wasp nests, 

 showing a great variety of architectural design, and pointed 

 out the opportunities for natural selection thus afforded. 



The following paper was read : — 



Catalogue of the Alcid^e contained in the Museum of 

 the Boston Society of Natural History, with a Re- 

 view AND PROPOSED CLASSIFICATION OF THE FAMILY. By 



W. B. Barrows. 



The Alcidse, or Auks, constitute one of four families of diving 

 birds; the other three being the Grebes, Loons and Penguins. 



In these three families the hind toe or ' hallux is present, while in 

 the Auks it is absent, they being the only three-toed divers. The 

 middle toe is longest, the outer one scarcely less, while the inner is 

 much the shortest. They are fully webbed and provided with 

 strong claws. Both tail and wings are short, the latter when folded 

 never reaching beyond the end of the tail. The legs are short, stout 

 and placed far back, rendering progression graceful and easy in the 

 water, awkward and difficult on land. The bill varies from ex- 

 tremely compressed to subulate, and in at least one instance is 

 almost depressed. The nostrils are lateral, and placed near the base 

 of the upper mandible. In life, the bill and feet are often brightly 

 colored, but the plumage is never brilliant, though the colors are often 

 strongly contrasted. The winter and summer plumages are usually 

 different, as are also those of the young and old birds, but sexual 

 differences of plumage have not been noticed. Twenty-one species 

 are now generally admitted by writers, and specimens of twelve of 

 these are contained in the Museum of this Society. From a thor- 

 ough study of these specimens, and a careful comparison of the 

 writings, descriptions, and figures of all the more reliable authors, I 

 have framed the following arrangement of the different genera and 

 species of the family. The reasons for adopting this arrangement, 

 and especially for the omission of the sub-families which most writers 

 have used, will be found in the remarks following the descriptions of 

 the genera and species. 



