. The sportsman's British bird book . of the group isthe great prolongation ofthe front portion of theupper extremity of thesecond segment of theleg, which forms a tri-angular spine projectingin front of the lower endof the thigh bone andaffording great leveragefor the muscles used inswimming and diving,this being specially neces-sary from the fact thatwhen diving these birdsimpel themselves by the hind-limbs alone, never making use of their wings when under waterafter the manner of petrels and auks. The hind border of the breast-bone has only a single notch on each side. The grebes generally
. The sportsman's British bird book . of the group isthe great prolongation ofthe front portion of theupper extremity of thesecond segment of theleg, which forms a tri-angular spine projectingin front of the lower endof the thigh bone andaffording great leveragefor the muscles used inswimming and diving,this being specially neces-sary from the fact thatwhen diving these birdsimpel themselves by the hind-limbs alone, never making use of their wings when under waterafter the manner of petrels and auks. The hind border of the breast-bone has only a single notch on each side. The grebes generally layfrom three to five eggs in a clutch, which are uniformly coloured andcoated with a chalky layer ; but the divers lay only two, which aredouble-spotted. The down-clad young are able to swim as soon ashatched. As regards distribution, the grebes have an almost world-wide range, but the divers, or loons, are restricted to the colder portionsof the northern hemisphere. All the members of the grebe-family, or Podicipedidae, are easily. GREAT CRESTED GREBE (FEMALE IN SUMMER). 224 GREBES AND DIVERS recof^niscd b\ the structure of the foot, in which the tliree front-toes arcfurnished with broad lateral lobes of membrane : unlike those of thecoots and phalaropes, these lobes are, however, united at the basesand are not contracted at the joints of the toes. The outermost ofthe three front-toes is the longest, and the hind-toe, which has smalllateral folds, is raised above the level of the others ; the claws areflattened, so as to resemble nails. Another ver} characteristic featureof the i^roup is to be found in the rudimentar\- condition or absence ofthe tail ; and there are twelve primary quills in the wing. In the skeleton it may be noticed that the lower jaw is not pro-duced backwards behind its articulation with the skull. As regardso-eneral habits, it may be mentioned that all these birds are essentiallyaquatic and, in summer at least, frequent frcshwaters, although inwinter they
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