THE MYRIAPODA OF NORTH AMERICA. 207 



Genus SPIROBOLUS. 



Scuti priini Iatera brevia, haud producta. Souti secundi latera longe prodncta, cum superficiebus anticis tri- 

 angulis. 



Sides of the first scutum short, not produced. Sides of the second scuta very much produced, with anterior 

 triangular surfaces. 



Sl'lROBOLUS, Brandt, Recueil, p. 114. 



The form and general appearance of this genus is very different from that of the true 

 lulus. The great size and thickness of the body, and the peculiar way in which the head 

 is set into it, so to speak, attract the first glance of the observer. The head is generally not 

 proportionally very large. The antenna? in our American species (except angusticeps ]) 

 are very short, and often lie almost hidden in a groove in the side of the head, bent so as 

 to form a right-angled " knee," with their free end directed downwards. 



The eye-patches are of various shapes, and, though large, are generally not very promi- 

 nent. The first scutum is broad, antero-posteriorly, with its sides more or less obliquely 

 truncate. The second scutum has its sides much produced and bent forwards, so as in a 

 measure to embrace the first scutum. Where it abuts against the head there is on each 

 side a triangular surface. 



In all the species which I have examined, the male appendages are formed after one 

 very peculiar type, with marked specific differences in the minutiae of their forms. This 

 may prove to be generic. In the true lulus no appendages have as yet been described 

 agreeing with this pattern. 



S. MARGINATUS. 



S. saturate brunneus, rubeo annulatus ; capite copiose minute punctato, antico punetorum maximorum serie 

 instructo; segmentis 53 — 57; scutis copiose minute punctatis; squama anale triangula. 



Deep brown, annulate with red; head copiously minutely punctate, furnished anteriorly with a series of large 

 puncta ; segments 53 — 57; scuta copiously minutely punctate ; anal scale triangular. 



Iulus marginatus, Say, Journ. Acad. Nat. Sci., 1st series, vol. ii, p. 105. 

 " " Gervais, Apteres, vol. iv, p. 180; Exped. L'Amer. du Sud (Castelneau), Myriap., p. 19. 



" " Brandt, Recueil, p. 89. 



S. MARGINATUS, Newport. 



? Iulus Americanus, Pal. Beauvois, Insect. Afrq. et Amer., p. 155, 



? Iulus incertus, Brandt, Recueil, p. 121. 



Iulus ornatus, Girard. 



? Iulus Atratits Girard, Marcy's Report, Expl. Red River of the South, p. "271. 



