12 PROCEEDINGS OF THE ACADEMY OF 



The wings are short. In no instance do thej', when folded, reach to the end 

 of the tail. In one species they are so undeveloped in their terminal segments* 

 that the power of flight is abrogated. The first primary is always longest; the 

 rest rapidly and regularly graduated ; all taper to a sufficiently fine point. The 

 secondaries are very short, and broadly rounded. The primary coverts are 

 very long, reaching much more than half-way from the carpus to the end of 

 the first primary. The first row of secondary coverts reach nearly to the end 

 of the secondaries. The under wing coverts are very long. The axillars are 

 short or wanting. The wing as a whole is convex above, concave below, nar- 

 row, sharp, stiff, somewhat falcate. These points of structure are constant 

 throughout the family. 



The tail is very short ; its length is contained, on an average, about three 

 times in the length of wing from the carpal joint. It is usually slightly round- 

 ed, sometimes nearly square, in a few instances pointed ; in a few more the 

 central rectrices are slightly shorter than the next pair. The individual feathers 

 are usually very obtuse at the end. Both sets of coverts are long ; the inferior 

 usually reach nearly or quite to the end of the tail. 



The feet are small, and placed far back, as has been said. The thighs are 

 contained within the general skin of the body. The legs are feathered nearly 

 or quite to the tibio-tarsal joint. The tarsus is short, sometimes excessively 

 abbreviated, rarely equal to the middle toe without its claw, never (?f ) longer. 

 It is usually much compressed, is sometimes almost as sharp as that of Coh/m- 

 1)UH, is frequently nearly as broad laterally as antero-posteriorly. Its covering 

 varies with different genera. It is usually reticulate behind and laterally, with 

 a row of scutellai in front, which rarely, however, if ever, extend its whole 

 length. In some genera it is entirely reticulate ; in others, the scutellation 

 extends on one or both sides. The tarsal envelope varies so much that it is 

 not available as a character for subdivisions higher than generic. The toes 

 are very long; the outer and middle always of nearly the same length ; the 

 inner shorter, its claw just reaching the base of the middle claw. There is no 

 hind toe. Dissection reveals the rudiment of a hallux, wiiich, however, is never 

 developed sufficiently to make even a well-marked prominence. The webbing 

 of the toes is complete. The claws are all moderately arched, compressed and 

 acute ; the inner edge of the middle is more or less dilated ; the middle is al- 

 ways the largest, except in two genera, which present the peculiarity of having 

 a very large semi-circular inner lateral claw, which, moreover, lies horizon- 

 tally instead of vertically. 



That rigid adherence to the type of structure just described which all the 

 species maintain, while facilitating the recognition of the family as a family, is 

 a serious obstacle in the way of defining its subdivisions with precision. With 

 no very abrupt transition from one form to another, and without any very 

 marked modification of general features, the minor groups seem to be formed 

 mainly by the varying combination of the few differences in structure which 

 obtain in the family. The assemblage of characters, rather than the presence 

 or absence of particular features, in most cases determines the genera ; and no 

 two species are absolutely alike in all points of form. 



" Facies non omnibus una. 



Nee diversa tamen, quails decet esse sororum." 



In one of the ablest papers that has appeared upon this subject. Professor 

 Brandt divides the Alcidx into two subfamilies: those with feathered, and 

 those with naked nostrils. In this arrangement the Guillemots stand next to 

 the typical Auk — A. torda. Viewed from any other standpoint the two forms 



* Cf. Mr. A. Newton's article in the "Ibis" for October, 18(i2. As there stated, the hu- 

 merus oi Alca impe.nnis is of normal size; the antibrachium, carpus and metacarpus, and 

 their quills, are shortened. 



^ Brack yrhampJius bracht/pterus is said by Brandt to have the tarsus longer tlian the middle 

 toe. 



[Jan. 



