NATURAL SCIENCES OF PHILADELPHIA. 209 



Southern, and essentially Antarctic. Nearly all Natalores are either largely 

 migratory, or else are widely wandering pelagic birds. 



Subdivisions of the Subclass.* 



Assembled in such variety of character, swimmers may be easily and con- 

 veniently divided in several ways, according to the standard taken. But I 

 presume only one of these can be the right {i. e. the natural) way ; and further, 

 that cceteris paribus, the scheme that takes into consideration the greatest 

 nunaber of characters will come nearer the truth than one that proceeds upon 

 isolated grounds. A sine qud non of any scheme must be equivalency of value 

 of the groups to which the same taxonomic rank is accorded. 



There is no safe stepping-stone between the subclass and its orders. There 

 are four orders, i. e., four modes of expression of the Natatorial plan or idea. 

 In the following definitions of these, diagnostic or more important characters 

 are italicized : — 



Ord. I. Pygopodes. — Legs jwsterior, horizontal position of axis of body impos- 

 sible ; most of cms as well as femur buried. Brachypteroiis ; wings short, 

 never reaching end oi very short, many-feathered tail, that is sometimes wanting. 

 Body depressed. Feet tetra- or tri-dactyle, lobatc or palmate, never totipal- 

 mate ; hallux elevated, functional or not. Bill not lamellate nor serrate ; wholly 

 corneous, entire. Nostrils lateral, mostly basal, well formed, never tubular. No 

 gular pouch. Tibia often with a long apophysis. Carotids single or double. 

 Schizognathous. Altrical or Prrecofial. Scarcely ambulatorial ; sometimes 

 not flying at all ; urinatorial ; swim under as well as on the water; lie deep on 

 the water. Heavy, clumsy on land. Natatorial Natatores. 



Ord. II. LoNGiPENNES — Legs near centre of equilibrium, horizontal position of body 

 usual. Femur buried ; crus largely (or wholly 1) free. 3Licropterous ; wings long, 

 pointed, surpassing the base, and often the tip, of the large well formed few-feathered 

 tail. Feet tetra- or tri-dactyle ; always palmate, never totipalmale ; hallux, when 

 present, free, elevated, very short, fanctionless. Bill ivholly corneou'*, entire or 

 pieced, unguiculate or not, 7iever laminate (exc. Prion, &c.) nor serrate. Nostrils 

 variously, but always well-formed,la.iQViil or superior. None, or only a rudimentary 

 gular pouch. Tibia with or without apophysis. Carotids double. Schizognathotts. 

 Altrices. The majority ambulatorial; all highly volucral ; none urinatorial; 

 all rest shallow and swim easily on the water. Light, elegant in all three 

 elements. f Volucral Natatores. 



Ord. III. Steganopodes. — Position of legs variable ; generally well posterior, 

 but sometimes approaching the preceding. Wings variable, but generally long 

 and pointed, approaching or equaling the preceding. Tail variable, sometimes 

 short and indefinitely feathered, usuall_v long and few-feathered ; cuueate 



* Reduce to an order, and pari passu reduce the value of subordinate group.s, if Saururse., 

 Ratitie and Carinatse be accepted as sub-classes. 



With such reduction in value, Insessores, Cursores and Naiaiorfs would become " orders" 

 of Carinatie. and the four " orders" indicated below would be suborders or "tribes," — i.e., 

 simply collocations of families. Throughout this article I call Natatores a "subclass " in 

 a conventional sense only, as indicating one of the first divisions of a class Aves, as 

 usually held. 



Even with this depreciation in the scale, I do not suppose that the Avian groups have 

 the value of those of the same name in other classes of vertebrates. Birds adhere so 

 closely to a common type, that the extremes of difference in form found among them 

 scarcely seem to indicate divisions of a higher grade than those marking orders in lower 

 vertebrates ; in fact, it is a question whether Aves as a whole are nriore different from some 

 other vertebrates than certain (''.^. reptilian) "orders " are from each other. But, how- 

 ever variously vertebrates may be primarily divided (as into Hiematotherma and Hiemato- 

 crya, into Icthhyopsida, Sauropsida, &.C., &c.), the four " classes" of Pisces. Rcplilia, Aves and 

 Mammalia will probably always endure, and be virtually our taxonomically equivalent 

 points of departure for further divisions. Therefore, as it seems to me, the rank of Nata- 

 tores only hinges upon the question of Carinalie, &c., as the primary divisions of Aves. 



t To most of these characters flatotiroma is a signal exception. But its tubular nostrils 

 define its position. 



1869.] 



