194 Bihl{o(jraphical Xofice. 42. Authors are urged to use only the metric system of -weights and measures and the centigrade thermometer of Celsius. 43. The indication of enlargement or of reductiou, which is necessary to the comprehension of an illustration, shoidl be expressed iu figures rather than by mentioning the system of lenses used. 44. It is useful to indicate whether the enlargement is linear, or of the surface, or of the mass. This may be easily expressed as follows: — X 50' indicates a linear enlargement of 50 times, x 5U* an enlargement of the surface, and x 50' an enlargement of the mass. BIBLIOGRAPHICAL NOTICE. Rhopcdocera Exotica ; heing Illustrations of Ntiv, Rare, and Un-Jjcjured Species of Butterflies. By H. (jrose-Smith and W. F. KiRBY. Vol. II. London : Gurney and Jackson, 1892-97. The second volume of this well-known work should have received notice at our hands before now ; but, as sometimes happens in the case of a serial publication still in course of issue, the fact of the volume's com])letion was overlooked. Unduly retarded, however, as our notice has been, the authors may rest assured that there is no lack of appreciation on our part of the manner in which the high standard ot their work has been maintained. As they mention in their preface, nearly 250 species are figured in this volume, the figures occupying sixty (]uarto plates, and representing not only both upper and under sides, but iu a large number of cases both sexes of each species. The colouring throughout is excellent, but the drawing of a few of the smaller figures is somewhat unequal in quality. It will be admitted, how-ever, that the best executed figures in point of drawing are those representing Oriental Lycaenidae (of the extremely beautiful genera Thi/sonotis, Waigeum, &.C.), which for accuracy as well as for artistic merit are admirable ; they are the work of Mr. Horace Knight. Butterflies of all families except the Hesperiidae find illustration in this volume : but in the number of species described and figuied the Lyctenidsp (10'-') far exceed the other groups. Xext come the
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