CALOTHORAX MICRURUS, Gow. Short-tailed Wood-Star. Calothoraxy nucrurus, Gould in Proc. of Zool. Soc., Noy. 22, 1853, reported in Athenzeum, Nov. 26, 1853. Tue members of the genus Calothorawx comprise some of the most diminutive of the Humming Birds, and the present species, as will be seen, is pre-eminently small. It differs from all its congeners in its extremely short and almost hidden tail; I might say entirely hidden tail, for the upper and under tail-coverts being longer than the tail itself, it is only when the little creature is on the wing and the tail spread to its fullest extent, that it can be seen. As in some other members of the genus, the feathers of which it is composed are stiff and rigid, especially in the male. The native country of this little bird is the interior of Peru, whence M. Warszewicz brought me examples of both sexes. All the information he could give me respecting them was, that they were quick fliers and loud hummers, and that they frequented the various species of Jdimosa. The Calothoraxy micrurus cannot be confounded with any species at present known, its characters being peculiarly its own. The male has all the upper surface mealy bronzy green; centre of the throat of a glittering amethystine hue; chin, sides of the throat and under surface buff, deepest on the sides; wings purplish brown ; tail black ; under tail-coverts white ; bill black. The female has the upper surface similar to that of the male ; the under surface buff, with a speck or two of the amethystine hue on the throat ; and the lateral tail-feathers tipped with white. The figures are of the natural size, on a species of Mimosa common in Peru.