is also the mediastinal vein on the front part of the organ. The numerous carboniferous Blattidae have been separated as a distinct Order of Insects by Scudder under the name Palaeoblattariae, but apparently rather on theoretical grounds than because of any ascertained important structural distinctions. He also divided the Palaeoblattariae into two groups, Mylacridae and Blattinariae, the former of which was supposed to be peculiar to America. Brongniart has, however, recently discovered that in the Carboniferous deposits of Commentry in France Mylacridae are as common as in America. This latter authority also states that some of the females of these fossil Blattidae are distinguished by the presence of an elongate exserted organ at the end of the body. He considers this to have been an ovipositor by which the eggs were deposited in trees or other receptacles, after a manner that is common in certain Orthoptera at the present day. If this view be correct these Carboniferous Insects must have been very different from the Blattidae of our own epoch, one of whose marked characteristics is the deposition of the eggs in a capsule formed in the body of the parent. In the strata of the secondary epoch remains of Blattidae have also been discovered in both Europe and America, in Oolitic, Liassic, and Triassic deposits. From the Tertiary strata, on the other hand, comparatively few species have been brought to light. A few have been discovered preserved in amber. [Illustration: FIG. 134.—Front leg of _Periplaneta australasiae_.] The classification of the Blattidae is attended with considerable difficulty on account of the numerous wingless forms, and of the {240}extreme difference in the organisation of the two sexes of many species. It has, however, been brought to a fairly satisfactory state by the reiterated labours of Brunner von Wattenwyl, and we reproduce his recently perfected exposition of their characters. His first division is made by means of a structure which is very easily observed, viz. whether the femora are armed with spines, as in Fig. 134, or not. The terms used in connexion with the wings and other parts of the body we have already explained. Brunner's system is adopted by de Saussure,[168] who, however, proposes to replace the names Ectobiides and Oxyhaloides by Anaplectinae and Plectopterinae. He also proposes to apply the generic name _Blatta_ to the Insect that is now so frequently called _Phyllodromia germanica_ in zoological works. If that view be adopted, Brunner's group Phyllodromiides will be called Blattides. Table of the tribes of Blattidae, after Brunner:— 1. Femora spiny beneath.[169] 2. The last ventral plate of the female large, without valves.