CHARACTERS OF PASSERES. 239 
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; fig. 
58). The bony palate has a peculiar structure, called egithognathous (fig. 79). There is but 
one carotid artery, the left (fig. 91). The cceca 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 anomalogonatous (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 of Passeres is altricial and psilopzedic (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, coérdinate with 
the rapidity of their. respiration and circulation ; they consume the most oxygen, and live the 
fastest, of all birds. They habitually reside above the earth, in the air that surrounds 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 394 are Passeres; as are more than half of all known birds. 
Passeres aze 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 differeuce 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 Oseines, 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 bilamimate, and the birds showing it are laminiplantar (figs. 37, 42, 43). In 
some cases the fusion of the tarsal envelope proceeds so far that 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. 86). The principal ex- 
ception to the association of a bilaminate or trilaminate tarsus with an acromyodian syrinx is 
afforded by the Alaudide, 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 arule. 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 with 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, are 
covered with variously arranged scutella, so that there is no sharp undivided ridge behind. 
