$Phrurolithus alarius.$--A small and very active spider marked with gray and white and having on the abdomen iridescent green scales (fig. 31). The cephalothorax is nearly as wide behind as it is long. The head is about half as wide as the thorax. The eyes (fig. 30) are large for so small a spider, and cover more than half the width of the head. The middle eyes of the upper row are oval and turned obliquely, diverging toward the front. The labium is short and the maxillæ straight, as in Agrœca and Anyphæna, but wider at the base (fig. 32). The legs are long and slender, except the tibia and metatarsus of the first and second pairs, which are twice as thick as the same joints of the other legs and have on the under side two rows of strong spines (fig. 29). The cephalothorax is light yellowish, with a black line on the edge each side, and two light gray stripes. The abdomen is gray, with transverse white markings that vary greatly in size and shape in different individuals. The abdomen is covered with scales that change from grayish green to pink with the motions of the spider. The legs are pale, except the patella and tibia of the first pair, which are black or dark gray, with the tip of the tibia white. The tibia and patella of the second pair are marked with lighter gray in the same way. It lives among stones in open ground, and runs short distances with great swiftness. When still it lies close to a stone, with the tibiæ drawn up over the back. [Illustration: FIGS. 33, 34, 35, 36. Agrœca pratensis.--33, eyes from in front. 34, maxillæ, labium, and ends of mandibles. 35, back of female enlarged four times. 36, under side of female as far back as the epigynum.]