488 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.50. 



Specimens from Massachusetts agree in all essential respects with 

 the original brief diagnosis by Tullberg and with the description by- 

 Carpenter, who compared his Franz-Josef specimens with Spitzbergen 

 examples sent to him by Dr. C. SchafTer. The Massachusetts speci- 

 mens belong to the variety concolor, but differ from Carpenter's 

 description and figures in having stouter antennal segments, uniden- 

 tate ungues and straighter mucrones. I sent some of these specimens 

 to SchafTer, who reported that they were dubius Tullberg, and changed 

 the name to tullbergi; the name dubius having been previously used 

 by Templeton for another species of Achorutes. 



I found large colonies of this species at Revere, Massachusetts, 

 August 23 and 25, under wet boards on a salt marsh. 



ACHORUTES MACGILLIVRAYI, new species. 

 Plate 13, figs. 74-81. 



Pale mottled blue above, pale beneath ; or uniform dark blue above. 

 Eye patches oval, remote from antennae. Eyes eight on each side. 

 Postantennal organs (figs. 74, 75) with four or five peripheral tubercles. 

 Antennae longer than the head, with segments as 7:8:9:20 in relative 

 lengths. Sense-organ of third antennal segment as in figure 76. 

 Unguis (fig. 77) feebly curving, inner margin unidentate one-third 

 from apex. Unguiculus one-half to three-fifths as long as unguis, 

 with broad rounded basal lamella, and with apical half acuminate. 

 Tenent hairs knobbed, 2, 3, 3 or 3, 3, 3, the middle hair larger than 

 the other two. Dentes subcylindrical, slender, untoothed. Mucrones 

 (fig. 78) one-fourth dentes in length, elongate-cuneate in profile, with 

 projecting blunt apex and dorsal subapical notch. Anal spines 

 (figs. 79, 80) two, about as long as the lamella of an unguiculus, stout, 

 almost straight, on large contiguous papillae. Clothing (fig. 81) of 

 sparse minute setae, with long stiff setae on the appendages and the 

 extremity of the abdomen. Length, 1.6 mm. 



This species resembles Achorutes purpurescens Lubbock, from 

 which it differs chiefly in the form of the mucrones and unguiculi and 

 in the type of clothing. Purpurescens, of which I have received six 

 European specimens from Dr. Caesar Schiiff er, has lon^ stiff setae in a 

 row across the middle of almost every body-segment which are lacking 

 in this species. 



Described from numerous cotypes collected at Ithaca, New York, 

 by Dr. A. D. MacGilhvray, after whom the species is named, and sent 

 to me some years ago by him and also by Prof. F. L. Harvey, of Orono, 

 Maine. 



New York. — Ithaca, April 18, May 2, September 4, November 

 12, under damp leaves and on surface of standing water, A. D. 

 MacGillivray. 



Illinois.— Galcsburg, March, on surface of lake, J. G. Needham. 



Cotypes.— Ci\t. No. 19900, U.S.N.M. 



