It is the misfortune of not understanding the typical structure, and the principles which regulate its variation, in higher groups, that in defining the characters of a lesser, we can form no just idea of its relative value: whether, in short, we should consider it a genus or a sub genus, or whether it is typical, aberrant, or osculent. This, however, is but a temporary evil; and will only continue until an insight is gained into higher combinations, by first placing together kindred species under one common name. If this be done heedfully, such a group _must_ be natural, whatever opinions may be entertained in the _first_ instance, as to its proper denomination. * * * * * * GENERAL INDEX _OF THE PLATES TO_ VOL. 1. IN THE ORDER OF PUBLICATION. ---- _N.B. The number here affixed to the Plates, for convenience of reference, had better be marked in pencil upon the Plates themselves._ No. 1. Psittaculus vernalis, 1 Polyborus Braziliensis, 2 Setophaga picta, 3 Ancillaria (Pl. 1.) rubiginosa, 4 Mitra (Pl. 1.) melaniana, 5 ---- tessellata No. 2. Parra Africana, 6 Cuculus nigricans, 7 Lorius Isidorii, 8 Ampullaria Pl. 1. ---- carinata, 9 Unio (Pl. 1.) truncatus, 10 No. 3. Thriothorus mexicanus, 11 Lorius garrulus, 12 Coccyzus Levaillantii, 13 Marmarostoma (Pl. 1.) ---- undulata, 14 Voluta (Pl. 1) ---- bullata, 15 No. 4. Paleornis Pondicerianus, 16 Hirundo fasciata, 17 Anodon (Pl. 1.) ---- areolatus, 18 Mitra (Pl. 2.) bicolor, 19 ---- carinata ---- strigata Tellina (Pl. 1.), 20 ---- latirostra No. 5. Nanodes venustus, 21 Icterus Cayanensis, 22 Drymophyla longipes, 23 Lingula anatina, 24 ---- hians, 25 No. 6. Platycercus scapularis, 26 Drymophila fasciata, 27 Aglaïa gyrola, 28 Melania (Pl. 1.) amarula, 29 ---- setosa Mitra (Pl. 3.) fulva, 30 ---- ambigua ---- punctata No. 7. Aglaïa flava, 31 Papilio Niamus, 32 Rhetus Cramerii, 33 Rostellaria (Pl. 1.) curvirostris, 34 Psaris Jardinii, 35