Genus SPIROBOLUS.
Scuti primi latera brevia, baud producta. Scuti secundi latera longe producta, cum superficiebus anticis triangulis.
Sides of the first scutum short, not produced. Sides of the second scuta very much produced, with anterior triangular surfaces.
Spirobolus, Brandt, Recueil, p. 114.
The form and general appearance of this genus is very different from that of the true Iulus. 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 antennæ 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 prominent. 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 minutiæ 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 punctorum 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 Sad (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 atratus Girard, Marcy's Report, Expl. Red River of the South, p. 274.
