The undulated brown lines in this shell, are sometimes broken into three irregular bands of either lines or spots, between which are numerous minute dots; in other varieties these dots are only round the suture, and in some totally wanting. Its most constant character rests on the umbilicus, which is rather large, very deep, and without any appearance of the base of the pillar. The mouth is also more contracted than usual. It is said by Adanson to be common on the coast of Senegal; and this observing naturalist adds, that the operculum is testaceous, of a pure white, and marked with numerous concentric grooves at the upper angle. * * * * * NATICA effusa. * * * * * _N. testa depressa, alba, maculis castaneis ornata; spira brevissima; columellae basi crassa, plana, ad labium interius sinu annexa._ Shell depressed, white, with chesnut spots; spire very small; umbilicus large, open, spreading; base of the pillar thick, flat, and united to the inner lip by a sinus. * * * * * In form, and sometimes in colour, this shell bears a close resemblance to the oval variety of N. mamilla (_Nerita mamilla Lin._); but, the umbilicus, instead of being entirely closed up, is remarkably open, very deep, and the pillar forming an elevated ridge within; colour in the shells of this genus is a very secondary, and, in many cases, a most fallacious guide for the discrimination of the species; for this is sometimes pure white, and I have specimens of _N. mamilla_ entirely orange. This is a rare shell, probably from India. * * * * * Pl. 105 [Illustration] TROCHILUS recurvirostris, _Recurved-bill Humming Bird._ * * * * * GENERIC CHARACTER.--See Pl. 82. * * * * * SPECIFIC CHARACTER. _T. aureo-viridis, jugulo smaragdino; pectore medio corporeque nigris; rectricibus lateralibus subtus topazinis; rostro recurvo._ Golden green; throat shining emerald green; middle of the breast and body black; lateral tail feathers beneath topazine; bill recurved. * * * * * The extraordinary formation in the bill of this beautiful little creature, is without parallel in any land bird yet discovered, and presents in miniature a striking resemblance to that of the Avoset. It is almost impossible to conjecture rightly the use of this singular formation; but it appears to me not very improbable, that the principal sustenance of the bird may be drawn from the pendent _Bignoniae_, and other similar plants, so common in South America, whose corollae are long, and generally bent in their tube; the nectar, being at the bottom, could not be reached either by a straight or incurved bill, though very easily by one corresponding to the shape of the flower.