792 SYSTEMATIC SYNOPSIS. — PYGOPOBES. 



middle of the back. The marking results from a small spot or stripe near the end of each 

 feather, on the edge of each web ; there is occasionally a second pair nearer the base of the 

 fciither. The amtumt of spotting is very variable with individuals; in the y(jiing the sjiots are 

 always larger and more numerous than in the adults, and usually lengthened into oblique 

 lines, producing a regular diamond-shaped reticulation. Northern Hemisphere at large; most 

 of the U. S. in winter ; breeds in high latitudes. Eggs 2-3, 3.00 X 1.75. 



62. Family PODICIPEDID^E : Grebes. 



Bill of variable length, much longer or shorter than head ; culmen usually about straight, 

 sometimes a little concave, or quite convex, especially at the end. Commissure nearly straight, 

 but more or less corresponding with the curve of the culmen, usually sinuate at base. Under 

 outline of bill in general convex, with slight gonydeal angle or none. Sides of bill more or 

 less striate. Nasal fosase well marked, the nostrils near their termination. Nostrils linear and 

 pervious (broader in Podilymbus), upper edge straight, not lobed. Frontal extension of 

 feathers considerable, and usually antia^ run still further into the nasal fossa. A groo-s-e along 

 the symphysis of the mandible extends often nearly to the tip. Eyes far forward, with a loral 

 strip of bare skin running thence to base of upper mandible, very narrow in the typical foniis,. 

 broader in Tachyhax^tes and Podili/mhus. Head usually adorned in the breeding season with 

 variously lengthened colored crests or rufi's : when these are wanting the frontal feathers may 

 be bristly. Neck usually long, slender, and sinuous. Plumage thick and compact, smoothly 

 imbricated above, below of a peculiar smooth, satiny texture. Wings slmrt but ample, very 

 concavo-convex ; primaries eleven, narrow, somewhat falcate, graduated, the three or four 

 outer ones attenuate on one or both webs ; secondaries short and broad ; tertials very long, 

 hiding the re-st of the quills when the wing is closed. Bastard quills imusually long, their tips 

 reaching over half-way to the ends of the primaries. Greater coverts also very brag. Tail 

 rudimentary, represented by a tuft of downy feathers. Characters of the feet iieculiar ; for in 

 other lobe-footed birds, as Phalaropes and Coots, the lobation is of a different character. Tarsi 

 exceedingly compressed, with only a slightly thickened tract within which the tendons pass. 

 Front edge a single smooth row of overlapping, the hinder ser- 

 rate with a double row of pointed, scales ; sides regularly trans- 

 versely scutellate, as are the upper surfaces of the toes, the latter 

 ^ "~ lll\ being inferiorly reticulate, with an edging of pectinated scales.. 



,a. Toes flattened out and further widened with broad l(d)es, espe- 

 cially wide toward the end, and at base conuectcd for a varying 

 distance by intcrdigital webs. Hind toe highly elevated, broadly 

 lobate, free. Claws short, broad, flat, obtuse, of squarish shajie ;: 

 that of the hallux minute. 

 ^ vAVlf! I The Grebes are strongly marked by the foregoing charac- 



ters, especially of the feet and tail, though they agree closely with 

 ll — -''" ' the Loons in general structure and economy. Pilncipal internal 

 characters are tho absence of one carotid, and of the ambiens, 

 femoro-caudal and accessory semitendinosus muscles, the greater 

 number of cervical vertebrae (19 instead of 13) and shortness of 

 Fig. mo his. — F. fibula; T the sternum, with lateral processes reaching beyond the transverse- 

 tibia, with re, its cnemiai process, main part (the reverse of the case in Loons). There is a long 

 nat size a, o a gre e, p^pjj.|jr|] process of the tibia, reaching high above th(! knee-joint, 



backed by a large jiatella of about equal altitude (fig. 53U Ins.). 

 The gizzard has a special piyloric sac; there are creca and a tufted oil-gland. Tlicse birds are- 

 expert divers, and have the curious habit of sinking back quietly into the M'ater wlien alarmed, 

 like Anhingas. Owing to the virtual absence of the tail, the general asjiect is singulai-, ren- 



