PROCEEDINGS OF THE NATIONAL MUSEUM. 



ably for one-fourth of their length, then increase shghtly in -vridth, 

 only to be again reduced in the posterior fourth. The claw is of 

 moderate size. 



The dorsal plate is in retraction less gibbous than in the majority 

 of species of this genus. 



Total length 143 /z; length of dorsal plate 90 /x, width 75 /x; length 

 of ventral plate 103 /i, width 58 /z; toes 32 /x, claw 7 //; width of anterior 

 points 62 pt; tail projects beyond dorsal plate 13 //. 



The description and measurements refer throughout to fully con- 

 tracted specimens. 



Type.— Cat. No. 16519, U.S.N.M., is from Glenburnie, Maryland, 

 where the species is abundant in Sphagnum. 



MONOSTYLA ACUS, new species. 

 Plate 36, figs. 1-3. 



In complete retraction the dorsal plate of the lorica is subcircidar, 

 with an anterior sinus of moderate depth, the sides of which form 

 nearly straight Hues. The ventral plate is oval and shghtly narrower 

 than the dorsal; the anterior sinus is of the same form as that of the 

 dorsal plate and projects very shghtly beyond it. The ventral plate 

 extends over the foot, beyond the dorsal plate, as a broad shield or 

 tail. The lateral sulci are deep, the posterior sulcus moderately so. 

 The lorica is without any markings. 



The first foot joint is roimded anteriorly and is, as usual in the 

 genus, immovable; the second foot joint is heart-shaped posteriorly 

 and squarely trmicate in front. The toe is approximately four-fifths 

 as long as the entire body, very slender and shghtly decurved at the 

 base; the claw is very long. There are three annular constrictions 

 of the mucus duct, the posterior annulus being about as far from the 

 end of the toe as the length of the claw, the second an equal distance 

 forward of the posterior, and the third about one and a half times 

 the length of the claw removed from the second. 



The dorsal plate is strongly gibbous posteriorly; the anterior por- 

 tion of the ventral plate bends downward in the center, as does also 

 the dorsal plate, so that they are in contact, and in a frontal view, 

 if such were obtainable, they would appear as a very broad V, of 

 nearly the same outhne as the anterior margin in dorsal view. 



Total length 180 /x; length of dorsal plate 85 ft, width 82 /x; depth 

 of frontal sinus 10 fx; tail projects beyond dorsal plate 15 /jl; length 

 of ventral plate 100 /x, width 72 /i; distance between inner edges of 

 lateral sulci 53 /j.; length of toe 64 pL, of claw 12 ^; greatest depth of 

 body 38 fx. 



Type.— Cat. No. 16520, U.S.N.M., comes from Glenburnie, Mary- 

 land, where the species is common in Sphagnum, growing in swampy 

 parts of the woods. 



