north of the western end of the railroad station (and the station is so close beyond the bridge that a small corner of the platform can be seen in the picture, beyond the right-hand abutment) an artificial rock exposure begins and extends nearly fifty yards westward, with unmistakable dips of forty degrees, south about fifty-three degrees west.

7. In the space, however, between the danger-post and the strongly marked dips of the eastern half of the eastern view, the structure is not so uniform, and is not so clearly shown by the photograph, nor indeed so easily made out on the ground. Ten yards along the cutting east of the danger-post and opposite the eastern end of a small stable on the top of the south side of the cut, and in the picture a little to the left or directly beneath the right-hand telegraph pole, in the rather smoothly rounded projecting rock mass, there is a small rock saddle, or anticlinal, that can be seen on the ground with some care, and can even be perceived in the photograph, especially where the layers about the midheight of the cut begin to bend over from the westerly dip. Six yards further east, on the western side of the first small depression or slight gully, and five yards west of the first strongly marked southwesterly dip surface, and in the picture almost directly below the telegraph pole, there is a small rock basin or synclinal, somewhat difficultly discerned in the photograph, yet still decidedly perceptible there with a little patience, particularly with the help of a strong magnifying glass, and quite visible on the ground. The partly obscure portion of the section, then, is at most a dozen or fifteen yards of the length of the cutting; and at right angles with the strike not more than eight or ten yards; and, as the photograph shows. it is apparently not the part represented by Prof. Lewis's sketch. It appears unfortunately impossible to make the dips of that portion extremely obvious in a photograph; but on the ground they can be seen with a little care, and have been distinctly recognized, not only by myself, but by Mr. Harden, and, in December, 1888, by Dr. Amos P. Brown and Mr. J. S. Elverson. The place is now so precisely pointed out that it can readily be identified by any one visiting the spot, and he can see for himself the accuracy of the description of the structure.

8. It is evident, then, that the rocks of the cutting are by no means fault rock, but merely steep-dipping and somewhat folded dark gray and dark red beds of the Gwynedd Shales, cut across at a sharp angle with the strike and much fractured with ordinary cleavage planes of many directions, and requiring for a perception of the structure to be observed at an angle of not more than forty-five degrees with the railroad instead of at right angles. The chief geological interest and value of the rock exposure, therefore, is not in its displaying a fault of otherwise incredible dimensions, with the unheard-of width of a hundred feet or more, and with the inconceivable heave of four or five miles for a nearly vertical trap dike; but in its showing how it may sometimes be a little difficult to distinguish the true bedding and dip among many confusing cleavage planes. The great fault, coming westward from the southern

edge of the island-like patch of paleozoic rocks near Doylestown, in fact does not go through the Chalfont cut at all; but nevertheless probably passes within a hundred yards north of it, as is shown by neighboring rock exposures on the other side of the fault and by changes in the color and character of the soil. There is no reason to suppose that the fault, great as it is, heaves in the least the trap dike that does probably exist pretty close north of it; and the trap that occurs within two miles and a half south of the fault at four or five miles to the east must undoubtedly belong to quite a separate dike. Instead of one great dike there seem to be several smaller ones not continuous nor quite in line.

On Apatela.

By A. Radcliffe Grote, A. M.

(Read before the American Philosophical Society, October 18, 1895).

The genus Apatela has awakened considerable interest on account of the diversity of types among the larvæ of the different species. As will be seen from my lists of the N. American species, these greatly exceed in number the European, and probably afford a larger number of these larval types; while nearly all of the European groups are represented in North America, the Agrotid fauna of the two continents being, as often insisted upon by me, closely related. It follows that our nomenclature is derived chiefly from European sources. It may be said that the Apatelidæ are difficult to distinguish from the Arctiidæ, by exclusive characters drawn from the imago.

I have only quite recently become acquainted with the extremely beau tiful work of Dr. T. A. Chapman, on the genus Acronycta (Apatela) and its allies, London, 1893, a publication which at once placed its author among the foremost of the students of the new Lepidopterology, a school which has entirely broken with the old system under which the study had become sterilized, and was in danger of passing entirely into the hands of fanciers and dealers, at least in Europe. The results of the New School may be estimated by the statement, that the spectres of the metaphysical groups "Bombycidæ," "Zygænidæ," "Noctuidæ," "Tineidæ," which, especially the former, haunted our nomenclature, have been effectually exorcised. The "Bombycida" have been shown to be composed of families belonging to no less than three superfamilies: Bombycides, Agrotides, Tineides; the results attained through phylogenetic and ontogenetic studies are now applied to classification.

In my list published in these Proceedings in 1883, I had separated the three families of which the "Noctuidæ " were then composed, and this classification is the basis of the catalogue published as Bulletin No. 44, of the National Museum, Washington, 1893. Recent studies of Mr. Harrison

G. Dyar show, that we must place my Thyatiride between the Geometrida and the Ptilodontidæ and divide the family* Noctuidae (a preoccupied name in Aves which I have accordingly rejected from the Lepidoptera) into two distinct families, upon larval structure, my Apatelidæ and Agrotidæ.

memna.

The families adopted by the new Lepidopterology may have exclusive characters offered in the larval stage. See Mr. S. H. Scudder's Historical Sketch, 103, where the statement is made, that generic distinctions are as easily traced in the larva as in the imago. If generic, then also family characters, since I have shown that the characters upon which all our divisions are based do not differ in essential respects Papilio, 3, 36, 1883. The family Apatelidæ has for its type Apatela aceris of Europe and includes, besides the typical genus Apatela (Apatele, Acronycta of authors), the genus Diphtera Hübner, 1806 (1811), with its type orion, to which genus our fallax belongs. Here belong also the genera Microcoelia and HarrisiOther genera included by me in May, 1895, my last list of our species, are probably correctly referred here, but Raphia is shown by Mr. Dyar to be wrongly included and should apparently be removed to the Agrotidæ near Episema. The larva of Leptina (Baileya) is unknown and this stage of several other genera incompletely studied, so that there will be some possible necessary changes. My last list had for its special object the fixing of the generic types and the restitution of the oldest rightful names. It had little or no changes in arrangement to propose; but I may mention here, that the genera Calocampa and Lithomoia should be classed by themselves under the tribe Calocampini Grt., 1890, taken out of the Orthosiini; while Lithophane and allies should not go with them, but remain in the Orthosiini, to which group they naturally belong. The question of whether we are to assign tribal or subfamily rank to these divisions of the Agrotidæ, has not been satisfactorily solved. But the possibility of a division into groups of the Agrotidæ is now virtually admitted, against Lederer's rejection of all such assistance to classification. More recently Hampson has proposed a division into subfamilies. The number of generic titles proposed for species of the genus Apatela in Europe is considerable and their correlation with structural groups a difficult task. I have applied to the names the historical method, with the result here noted. The subgeneric groups here proposed are of unequal, and in some cases, i. e., Arctomyscis, of doubtful value. Yet there is no reason for their rejection without very careful study, above all of the American species which may throw fresh light upon their standing. In the case of Jocheæra, the discovery of the American funeralis assists the view that the group is natural and therefore valid. The clubbed hairs are peculiar, reminding one of the primary hairs of Saturnia pavonia major. *See my Systema Lepidopterorum Hildesiæ, August 15, 1895. Since then I have received Dr. Chapman's papers which show the affinity of the Cossidæ and Tortricidæ, the former family should therefore immediately precede the latter. The family Eriocephalidæ should be added at the last. For this Packard quite recently proposes the suborder Lepidoptera laciniata.