1. _Willughbiella_, Kirby, ♂♀. 5-7 lines. 2. _maritima_, Kirby, ♂♀. 6-7 lines. (Plate XII. fig. 2 ♂♀.) 3. _circumcincta_, Kirby, ♂♀. 4½-5½ lines. §§ _Anterior tarsi of males not dilated._ 1. _ligniseca_, Kirby, ♂♀. 5-7 lines. 2. _centuncularis_, Linnæus, ♂♀. 4-6 lines. _centuncularis_, Kirby. 3. _argentata_, Fabricius, ♂♀. 3-4½ lines. (Plate XII. fig. 3 ♂♀.) _Leachella_, Kirby. _Leachella_, Curtis. 4. _odontura_, Smith, ♂. 4½ lines. GENERAL OBSERVATIONS. Named from the great development of the labrum, _μέγα_ _large_, _χεῖλος_ _lip_, which is characteristic of all the _Dasygasters_, and also of some of the proximate _Nudipedes_, those parasitical upon them, _Stelis_ and _Cœlioxys_, and which, too, resemble the sitos in the expansion and dentated formation of their mandibles, although they do not use them for the same purposes; this again exhibits an analogy of structure, that appears in the parasite to be merely corroborative of identity of existence. These are more essentially summer insects than the majority of the preceding genera, although some of them present themselves with genial spring weather. The genus may be separated into two distinct divisions by the peculiar dilatation of the tarsi of the males of some of the species, but such division is not indicative of a difference of habits, as is distinctly the case in the genus _Anthophora_, and in which these combined circumstances Mr. Kirby suggested as acceptable for generic division, or, as he called it, the institution of another _family_. But in these we find in both divisions both wood-borers and earth-tunnelers, and some species are indifferently either as suits their accidental convenience. The general appearance of the insects is more that of ordinary bees, and the sexes are more approximate in their habit than is usually the case. With this genus commences essentially those designated as artisan bees, although _Colletes_ might very suitably come under that denomination. The species themselves of the genus are called leaf-cutters, from the habit they have of cutting pieces from the leaves of various shrubs and trees, for the purpose of lining their nests. The description of the operations of one species will apply precisely to that carried on by all, the occasional difference between them being the selection of the leaves of distinct plants; and it will exhibit the patient industry and perseverance with which these little upholsterers carry on their labours.