196 THE MYRIAPODA OF NORTH AMERICA. 



well adapted for active service. The second scutum is never produced forwards at the 

 sides so as to abut against the head, as in Spirobolus. In all the species in winch I have 

 had an opportunity of examining sexes, the form of the first scutum distinguishes them 

 with certainty. In the male its antero-posterior diameter is large, and there are well- 

 marked lateral margins running nearly at right angles to the others. In the female the 

 anterior posterior diameter is much less, but laterally the scutum is so produced that the 

 anterior and posterior margins may in most eases he said to meet one another at an .angle. 

 The males are further distinguished by a peculiar alteration of the first pair of feet, which 

 are transformed into a pair of very large, thick organs. The function of these is obscure, 

 hut possibly it may be connected with the union of the sexes, analogous to that of the 

 "claspus" in some reptiles. 



I. IMPRESSES. 



I. rubro-castaneus, linea dorsale nigra et macnlae nigne seriebus Iateralibus (interdum obsoletis) ornatus; anten- 

 nis Iongis, h'liformibus, pilosis, baud clavatis ; scutorum latevibus canaliculars; segmentis 52; mucrone parvo. 



Reddish chestnut, ornamented with a black dorsal line, and a lateral series of black clots (sometimes obsolete) ; 

 antenna; long, filifurm, pilose, not clavate; sides of the scuta canaliculate; segments 52; nuicro small. 



I. impressus, Suy, Journ. A. N. S , 1st series, vol ii, p 102. 



Gervais, Apteres, vol iv, p. 176; Exped. L'Auicr. du Sud (Castelrie.au), Tabl. Myriap., p. IS ; 

 Brandt, Recueil, p. 81. 



I. venustus, Wood, Proo. Acad. Nat. Sci., lstjl, p. 10. 



The general color of this species is reddish chestnut; frequently the red predominates 

 so much that the individual is really flesh-colored, but occasionally the chestnut over- 

 comes the other tint. The dorsal stripe is generally very distinct, especially on the poste- 

 rior portion of the scuta. The eyes are triangular, and are connected by a dark band, 

 which is often rather obscure. The anterior cephalic aspect is long and narrow, with its 

 sides converging inferiorly. Its inferior border is fringed with a double row of short, 

 distant hairs, and is medianly deeply emarginate, and 2 — 4 dentate. The scuta are orna- 

 mented, rarely with a white blotch on each side of the mesial line, but generally with two 

 lateral black dots. The first scutum in the female has the anterior margin oblique as to 

 the main axis of the body, and is prolonged laterally so as to firm processes, mostly canali- 

 culate, with a. rounded border. In the male the anterior margin is at right angles to the 

 axis of the body, and the lateral parallel to it, so that there are no processes. The male 

 appendages consist of two main portions on each side. The outer and more conspicuous 

 ol these ( Figs. 27, 28) is formed of a thin, very irregular plate, from whose base springs a 

 short, clavate, cylindrical, distally pilose process. The inner portion (Fig. 26) is composed 



