CHARACTERS OF PASSEBES. 289 



pigeons, nor cered, as in parrots and birds of prey. The nostrils do not openly communicate 

 with each other. The oil-gland (p. 86) is nude, and of a characteristic shape. Besides these 

 external characters, which the student may readily examine without dissection, there are some 

 more important anatomical ones. The sternum (with few exceptions) is cast in a particular 

 mould, being manubriated, with prominent costal processes, and having each side of the poste- 

 rior border single-notched (neither entire, nor deeply nor doubly notched, nor fenestrate ; tig. 

 58). The bony palate has a peculiar structure, called aegithoguathous (fig. 79). There is but 

 oue carotid artery, the left (fig. 91). The coeca coli are present, though small. There is a 

 peculiarity in the method of insertion of the tensor patagii brevis. Besides possessing the pecul- 

 iarity of the flexors of the toes, already mentioned, Passeres are anomalogouatous (p. 195) ; 

 that is, the ambiens muscle is absent, as is the accessory femoro-caudal; the femoro-caudal and 

 semitendinosus are present, as is usually also the accessory semitendinosus. 



Physiologically, the nature oi Passeres is altricial and psilopisdic (p. 88) ; that is, the young 

 are hatched weak and naked, and require to be fed for some time in the nest by the parents. 

 They represent the highest grade of physiological development, as well as the most perfect 

 physical organization of the class of birds. Their nervous irritability is great, coordinate with 

 the rapidity of their respiration and circulation ; they consume the most oxygen, and Uve the 

 fastest, of all birds. They habitually reside above the earth, in the air that suiTounds it, among 

 the plants that with them adorn it; not on the ground, nor on " the waters under the earth." 



Pas'seres were named by Cuvier in 1798 as an order of birds ; the name is simply the 

 plural of the Lat. passer, a sparrow. But the group as established by him included many 

 forms which were first properly excluded by the celebrated Nitzsch, who in 1829 limited the 

 group as now accepted. Besides being one of the best defined, it is by far the largest group 

 of its grade in ornithology. For example, of the 888 birds enumerated as North American in 

 the Check List, no fewer than 894 are Passeres; as are more than half of aU known bmls. 



Passeres are primarily divisible into two groups, commonly called sub-orders, mainly 

 according to the structure of the vocal organ, — the lower larynx, or syrinx. In one of these 

 groups, the musical apparatus is highly developed, with several distinct pairs of intrinsic mus- 

 cles, inserted into the ends of the upper three half-rings of the bronchial tubes. In the other, 

 the voice-organ is less complex, with less specialized muscles inserted into the middle portions 

 of the upper bronchial half-rings. The former arrangement is termed acromyodian, the latter 

 mesomyodian : and the birds which exhibit this difiereuce of structure are respectively called 

 Passeres acromyodi and Passeres mesomyodi, or Oscines and Clamatores. (See p. 205, fig. 101.) 



Associated with the acromyodian or oscine type of syrinx is a peculiar condition of the 

 tarsal envelope. In nearly all Oscines, the tarsus is covered on each side with a horny plate, 

 nearly or quite undivided, meeting its fellow in a sharp ridge behind. This condition of the 

 tarsus is called bilaminate, and the birds showing it are laminiplantar (figs. 37, 42, 43). In 

 some cases the fusion of the tarsal envelope proceeds so far tliat the front of the tarsus likewise 

 presents a nearly or quite undivided surface, the whole tarsus being then encased in a "boot," 

 as it is called. A " booted" tarsus may be said to be trilaminate (fig. 36). The principal ex- 

 ception to the association of a bilaminate or trilaminate tarsus with an acromyodian syrinx is 

 afforded by the Alaudidce, which have the tarsus scutellate and blunt behind; and, with very 

 few exceptions, no bird which is not acromyodian has a bilaminate tarsus. A third important 

 feature characterizes Oscines, as a rule. This is the reduction in length of the first primary, 

 which never equals the longest primary in length, is rarely over two-thirds as long as the 

 longest, is so short as to be called spurious, or is quite rudimentary and apparently wanting, 

 leaving apparently only nine primaries (fig. 30). 



Associated vnth the mesomyodian or clamatorial type of syrinx is seen (with few excep- 

 tions) the opposite condition of the tarsus, the sides and back of which, as well as the front, arc 

 covered vidth variously arranged ecutella, so that there is no sharp undivided ridge behind. 



