1904.] NATURAL SCIENCES OF PHILADELPHIA. . 319 



cephalothorax has a broad submarginal white band on each side, con- 

 tinued also across the forehead. 



Comparisons. — There is no doubt that this is the urinator of Hentz ; 

 it possesses the pairs of small white spots on each posterior abdominal 

 dorsum, and the slightly curved black lines (not of the shape of a W) 

 connecting them, all shown distinctly in Hentz's figure. It is closely 

 related to fontanus, and the epigyna of the two are very similar, but in 

 urinator it is always much broader than long, and its median piece has 

 a transverse groove just behind the middle, while in fontanus it is nearly 

 as long as broad and is without such a groove. There are a number of 

 constant differences, expressed in the key, which will serve to separate 

 the species. The females of idoneus may be easily distinguished from 

 those of both urinator and jonianus by the entirely different structure 

 of the epigynum, and by leg IV being longer than I by less than one- 

 third the length of the terminal joint. 



Dolomedes idoneus Montgomery. 



Dolomedes idoneus Montgomery, 1902. 

 ?Dolomedes tenebrosus Hentz, 1841. 



( 9 9 from Pennsylvania, New Jersey and Massachusetts.) 



Eyes. — First row broader than the second, its middle eyes shghtly 

 larger and decidedly lower than the lateral (the dorsal margin of the 

 middle eyes extends dorsad to a little beyond the level of the ventral 

 margin of the lateral eyes), lateral eyes quite twice their diameter in 

 front of the eyes of the second row. Eyes of the second row not quite 

 their diameter apart. Third row broadest, its eyes on tubercles. 

 Quadrilateral of the middle eyes as broad as long. 



Form ( ? ) . — Cephalothorax in front truncated straight, not quite 

 one-half its greatest transverse diameter, the cephalic portion demar- 

 cated from the thoracic, highest at the posterior eyes. Chelicera with 

 4 ventral and 3 dorsal teeth. Labium as in urinator. Sternum 

 slightly longer than broad. Legs rather slender, IV, II, I, III, IV and 

 II nearly equal in length. Length of leg IV to cephalothorax as 4.1 : 1. 



Comparisons. — Of all of Hentz's species this most nearly approaches 

 his tenebrosus. But as I wrote before (1902), Hentz's description is 

 entirely insufficient as a diagnosis; further, he placed tenebrosus under 

 the 'Henebrosse" with the "eyes subequal, lower row as much curved 

 as the upper," which is not the case in idoneus; and his figm-e of the 

 mouth parts shows them entirely different from the condition in idoneus. 

 It is high time that tenebrosus, which has occasioned so much dispute, 

 should be allowed to fall into the synonymy on account of being 

 insufficiently characterized. 



