212 kobert h. wolcott: 



near that city ; and Unio luteolus, from White Lake, Muskegon 

 County, Mich. The dates were from July 27th to August 30th. 



3. ATAX PECTINATUS WOLCOTT. 



Atax pectinatus Wolcott, 98; 280. 



A species, in the character of the genital area allied to A. crassipes 

 and A. figuralis Koch, but with the legs relatively shorter than either and 

 with the palpi very thick, considerably thicker than the basal segment of 

 the first pair of legs. The claw of this pair of legs is broad, flat and 

 deeply pectinate, which character suggests the specific name. 



It is of medium size as compared with the other species of the genus, 

 the males measuring 0.7 to 0.8 mm., the females 0.8 to 1.0 mm. in length 

 respectively. The body is broadly elliptical with the antero-posterior 

 diameter but slightly greater than the transverse, which is greatest at a 

 point about midway between the anterior and posterior extremities. The 

 posterior margin is smoothly rounded and the surface is uniformly 

 smooth and without chitinous thickenings of any kind. The males are 

 somewhat slenderer than the females. 



Eyes moderate in size, with the anterior of the two lenses the larger. 



Maxillary shield relatively short and broad, with a prominent rostrum 

 formed by the apposed anterior mesial angles of each of the two max- 

 illary plates which are completely fused anteriorly. The posterior lateral 

 angles are quite evident though rounded while the ancoral process pro- 

 duced by the apposition of the two produced posterior mesial angles is, as 

 compared with other species, very weak. 



Mandibles with a long, narrow proximal segment which is slightly 

 broader posteriorly where it is directed somewhat ventrad and tapers to 

 a bluntly rounded point, in front of which is a shallow mandibular groove. 

 Its form is irregular owing to the undulating marginal outline. Distal 

 segment large, with a bx-oad basal portiou and a sickle-shaped claw which 

 is moderately curved except toward the tip, where the curvature is more 

 pronounced and where it tapers somewhat more rapidly than before to a 

 sharp point. The proximal half of this claw is marked by fine, wavy, 

 oblique lines. Extreme breadth equal to about one-fourth its total length. 



Palpi large and heavy, those of the female somewhat more than two- 

 fifths the length of the body. Those of the male are very little smaller than 

 those of the female in absolute measurement and are therefore larger* in 

 proportion to the size of the body. Basal segment short and broad. Segment 

 2 is the largest and much the thickest, equaling nearly one-half the total 

 length and with a thickness in proportion to the length as 5:9. The flexor 

 side is nearly straight, with a very slight concavity, the extensor side very 

 convex and evenly so, making it much longer than the other and causing 

 the planes of the two ends to be very oblique to one another. On the 

 inner side of segment 2 are two flattened spines rather near together, at 

 a distance from the basal margin of about one-third the length of the seg- 

 ment, and a third one-half the distance from these to the distal end, all 

 three being nearer the extensor than the flexor side of the palpus. On 



