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the swifts and humming birds. In Chatura, Cypselus,' and Phaethornis and other humming birds the tensor brevis is fleshy for almost its whole extent. In Dendrochelidon the tensor brevis has still a larger muscular portion than is usual, but the tendon is more evident and has a passerine slip to the humerus. In the Trochili, however, the muscle is inserted on to a special tendon upon the fore arm, and not on to the extensor metacarpi. In the leg muscles the birds of this group agree in only possessing the femorocaudal of those used by GARROD in his classification; the formula, therefore, is A. GARROD, however, has left a note to the effect that in Chatura caudacuta the femorocaudal passes through a muscle arising from both pubis and ischium, which is thus possibly a combined semitendinosus and semimembranosus.

Though the semitendinosus is as a rule absent, there seem to be traces of its accessory in a few swifts. Thus in Cypselus alpinus and Chatura Vauxi the gastrocnemius has an origin between the biceps loop and the main body of the sciatic nerve from the femur.

Another peculiarity in the leg of certain swifts (cf. also Phaëthon) is the absence of a biceps loop; but the value of this character may be gauged from the following table

Without Biceps Sling

Chatura caudacuta

Panyptila melanoleuca
Dendrochelidon coronata

Macropteryx mystacea

With Biceps Sling

Chatura spinicauda

Chatura zonaris

Cypseloides fumigatus
Cypselus alpinus

The biceps femoris of humming birds-at any rate of Patagona gigas-is peculiar in the fact of its being twoheaded.

The deep flexor tendons in the swifts vary. In the majority of forms the two tendons completely blend; in

1 For Cypselus muscles see NITZSCH-GIEBEL, Zur Anatomie d. Mauerschwalbe,' Zeitschr. f. d. ges. Nat. x. 1857, p. 327.

2 This tendon locks like a degenerate representative of the abductor pollicis.

1

Macropteryx, however, LUCAS has described the flexor hallucis as going to the first digit only after giving off a vinculum to the tendon of digit IV. As to the humming birds, there has been some confusion. It appears, however, that the flexor hallucis before going to digit I. gives off a slip to flexor communis of digit II., and (according to GADOW 2) III. and IV. also.

Both swifts and humming birds have, as a rule, only one carotid, the left. The following swifts have two carotids: Chatura rutila (right carotid larger), Cypseloides fumigatus. In Micropus (? Panyptila) melanoleuca SHUFELDT has described the left carotid (the only one present) as crossing over to the right and being until the middle of the neck free of the hypapophysial canal.

The chief peculiarity of the vascular system concerns the femoral vein. In Panyptila melanoleuca and in Chatura zonaris the femoral vein, instead of running deep of the femoro-caudal muscle, comes to join the sciatic artery and nerve immediately it has passed the obturator externus superficial to the femoro-caudal tendon; Cypseloides fumigatus is the only other swift which has been shown to be characterised by this structural abnormality.

The large size of the heart of the humming birds as compared with that of the swifts is commented upon by SHUFELDT.

The syrinx of the swifts is not in any way remarkable ; it is tracheo-bronchial, with the usual pair of intrinsic and extrinsic muscles. The former are attached (at any rate in Chatura caudacuta) to the first bronchial semi-ring. In Cypseloides fumigatus, however, a swift which is in other ways abnormal, there appear to be no intrinsic muscles.

The humming birds, on the contrary, have an unusual form of syrinx, which is remarkable in two ways.

In the first place the trachea bifurcates very high up in the neck, recalling the characteristics of Platalea rosea (see below). Each bronchus in Trochilus colubris (according

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to MACGILLIVRAY!) has as many as thirty-four rings, which are complete and not semi-rings. There seem to be two pairs of extrinsic muscles, which form a very prominent muscular mass, as in Passeres. Dr. SHUFELDT was unable to find any sterno-trachealis.

The tongue in the swifts is short and sagittate, with a spiny base. It is constantly bifid at the tip.

In the humming birds, as is well known, the long tongue is tubular, and for its support the hyoids are bent over the top of the skull, as in the woodpeckers. The tongue itself 'is double right down to the unpaired part of the os entoglossum, whilst each of the two distal prolongations of the entoglossal bone or cartilage is surrounded by a horny sheath, which is curled upwards and inwards, in a similar fashion to what we have seen in the Nectariniidæ.

In many species the outer and inner edges of these tubes, however, are entire and not laciniated. Thus the Trochilidae have developed the highest form of tubular tongue' (GADOW 2).

The gizzard of the humming birds is remarkably small; that of the cypselids presents no remarkable characters, and SHUFELDT has remarked upon the large size of the liver in the humming birds as compared with the swifts; in both the right lobe is larger than the left, and there is a gall bladder in the swifts.

Cæca are entirely absent in the Macrochires.3

following are intestinal measurements of the swifts:

Cypselus apus

Dendrochelidon coronata

Chatura caudacuta

Cypselus alpinus

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The

Chatura Vauxi .

A careful account of the trochiline and cypseline skeleton will be found in a memoir by SHUFELDT. Though this

1 In AUDUBON'S Birds of N. America.

2 On the Suctorial Apparatus of the Tenuirostres,' P. Z. S. 1883.

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3 CRISP, On some Points relating to the Anatomy of the Humming Bird (Trochilus colubris),' P. Z. S. 1862, p. 208, observed a rudimentary appendix.' 4 Contribution to the Comparative Osteology of the Trochilidæ, Caprimul

observer is disinclined to allow a very near affinity between the birds, it is undeniable that there are resemblances. The skull is schizognathous in the humming bird, ægithognathous in the swifts. But the agithognathism in the latter is a little abnormal. GARROD has pointed out in describing the osteology of Indicator that that bird, in common with the Capitonidæ, has a truncated vomer, in which the truncation occurs behind the line joining the maxillo-palatines, while in the true Passeres the truncation is in front of this line. The swifts are intermediate, the truncation being, as is shown in the accompanying figure (fig. 104), about on a level with the line joining the maxillo-palatines. It is true that the lateral processes so characteristic of the ægithognathous skull are better developed in the swifts than in the swallows; but, on the other hand, it must be borne in mind that the undoubtedly ægithognathous Indicator is without these processes. In both swifts and humming birds the skull is

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FIG. 104.-SKULL OF Micropus melanoleucus. UNDER

holorhinal and without basipterygoid VIEW. (AFTER SHUFELDT.)

As to the vomer,

Pmx, premaxilla; Mrp, maxillopalatines; Vo, vomer; Na, nasal; Pl, palatine; Pt, pterygoid.

processes. HUXLEY described it as truncated; but SHUFELDT finds it to end in an excessively fine point. In swifts the vomer is, as already stated, truncated. But as to this difference and its value as a means of separating the birds cf. the manifold vomer of Limicolæ.

The humming birds have fourteen or fifteen (Trochilus Alexandri) cervical vertebra. The Cypselidæ have thirteen or fourteen. Four ribs 2 join the sternum on each side

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gidæ, and Cypselidæ,' P. Z. S. 1885, p. 886, and 1886, p. 501. See also ZEHNTNER, Beiträge z. Entwicklung von Cypselus melba,' Arch. f. Naturg. lvi. 1890, p. 189 (transl. in Ibis, 1890, p. 196).

1 Loc. cit. (on p. 196.)

2 FÜRBRINGER says five or six.

in both groups of birds. The sternum in both is unnotched and broader behind than in front.

In the fore limb the length of the hand distinguishes

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name.

Pf, pneumatic fossa.

FIG. 106.-PALMAR ASPECT OF SAME
BONE (AFTER SHUFELDT).

both the families of the Macrochires, whence, of course, the The nearest approach in length of hand is shown in the swallows, petrels, and, oddly enough, in the penguins.

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The humerus in both families is extremely short; the radial crest is well developed in both into a long process which curves over the shaft in the Trochilidæ, but over the head in the swifts.

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