SYNOPSIS OF NORTH AMERICAN MTRIAPODA. 237 



P. comujatus. Blackish chestnut, with yellowish lateral laminae, and the scuta pos- 

 teriorly margined with yellow. 



P. bifidus. Reddish chestnut, with yellowish lateral laminae and the scuta both ante- 

 riorly and posteriorly margined with yellow. 



P. trimaculatus. Deep reddish brown, with three bright orange spots on each scutum. 



P. crassicutis. Very large. Scuta irregularly subrudely punctate. 



Subgenus Leptodesmus. 



Dorsum strongly convex. Lateral laminte small. 



P. placidus. Olive brown. Scuta banded with black. Lateral laminte light brown. 

 P. Jloridus. Blackish chestnut ; scuta margined posteriorly with reddish orange. 

 Lateral laminae orange. 



P. Haydenianus. Olive chestnut. Lateral laminte yellowish. 



Subgenus Strong ylosom a. 



Body cylindrical. Lateral laminte very small. 



P. eruca. 



Fam. IULID^. 



Posterior subsegments, with their sterna atrophied. Segments numerous, without late- 

 ral laminae. 



Genus Iulus. 



The second scutum not produced anteriorly at the sides so as to abut against the head. 



a. Last scutum mucronate. 

 * Mucro small. 



I. imjjressus. Reddish chestnut. Segments 52. Scuta scarcely at all pilose. 



I. pilosiscuta. Brownish chestnut. Segments 58. Scuta very pilose. 



I. Oregonensis. Bright chestnut. Segments 45. Scuta scarcely at all pilose. 



** Mucro large. 

 f Mucro uncinate. 



I. Canadensis. Brightish chestnut, with a black dorsal stripe and series of black dots 

 on each side. Segments 53. Mucro very large. 



I. immaculatus. Dark reddish brown, immaculate. Segments 51. Mucro moderate. 



f f Macro straight, or nearly so. 



I. Pennsylvanicus. Segments 63. Scuta on the upper surface distantly and obsoletely 

 canaliculate. 



