1. _cærulea_, Villers, ♂ ♀. 2-3 lines. (Plate VII. fig. 3 ♂ ♀.) _cyanea_, Kirby. 2. _albilabris_, Fabricius, ♂ ♀. 2½ lines.
This genus is named from the presence of a little horn between its antennæ, _κερατίνη_, _a horn_. Some foreign entomologists, especially Latreille and Le Pelletier de St. Fargeau, have considered it to be parasitical, but that it is not so we have the authority of the Marquis Spinola, of Genoa, confirmed by the testimony of Mr. Thwaites, a very accurate observer, in the vicinity of Bristol, where the insect is not at all uncommon, although extremely rare in most other parts, and consequently usually a desideratum to cabinets, from its great beauty both of form and colour, notwithstanding that it is so very small in size. It has also been found in other localities, as at Birchwood, where the late Mr. Bambridge used to take it, and as near London as Charlton, at both which places I have no doubt it might frequently be found were it carefully looked for, but the practised entomological eye is often wanting to detect an insect unless it be conspicuously present. Its usual nidus is a bramble or briar stick, from which it excavates the pith, and this it has been frequently observed doing, and both sexes have been repeatedly bred from such sticks. We have no notice of any peculiarity in its mode of forming its cells, which may resemble that of such wood-boring genera as _Chelostoma_ and _Heriades_, although its structure would intimate a closer affinity to the habits of the exotic genus _Xylocopa_; nor is there extant any account of the process or time occupied in the development of its young. Spinola’s notion, from not seeing the sufficiency of the hair upon the posterior tibiæ for the purpose, assumed that the pollen was conveyed home on the forehead and between the antennæ, he having caught an insect with some pollen accidentally incrusted there in the insect’s honey-seeking excursion. The hair upon these legs is very sparse, it is true, but then it is very long, and the quantity of pollen required for the nurture of the larva is evidently small, from its having been observed that the store upon which the egg is deposited is semi-liquid, thus preponderating in the admixture of honey.