48 BULLETIN 46, UNITED STATES NATIONAL MUSEUM. 



Genus II. — Spirobolus Brandt. 



Spirobolus Brandt, Bull. Soc, Imp. Nat. Mos., 202, 1833. 

 The subgenera are defined as follows : 



a. Basal part of the dorsal plates without scohina Spirobolus Karsch. 



aa. Basal part of the dorsal plates with scohina Ehinocrinus Karsch. 



Subgenus Ehinocrinus. 



5. Spirobolus marginatus (Say). 



Jiilus marginatus Say, Journ. Acad. Nat. Sci. Phila., 105, 1821. 

 Spirobolus marginatus Wood, Traus. Amer. Philos. Soc, 207, 1865. 



Dark brown; segments edged with brownish fuscous ; first and last 

 segments green or brown; feet and antennae brownish-red. Eobust, 

 not attenuated anteriorly, the anterior four or five segments somewhat 

 depressed, not smooth. Vertex smooth, with faint reticulating lines, 

 sparsely punctate, most numerous between and behind eyes; median 

 sulcus interrupted ; clypeal foveohe 8-10. Antennae short, not reach- 

 ing the posterior border of first segment. Eyes indistinct, sub trian- 

 gular; ocelli, 30-40, arranged in 6 series. Segments, 47-52. First seg- 

 ment with the sides subacute, marginate, the anterior border nearly 

 straight, densely jmnctate ; second segment produced forward into a 

 moderately large subquadrate plate. Other segments equally punc- 

 tate on both divisions, striae moderate, decurved beneath. Last seg- 

 ment pointed, but not extending beyond the anal valves, finely punc- 

 tite; anal valves marginate; punctate; anal scale obtusely angled, 

 punctate. Repugn atorial pore placed on the anterior division, large, 

 transverse suture bent. Pairs of feet, 88-100, extending beyond the 

 sides of body. Male : the two anterior pairs of feet more robust than 

 the rest; coxae of the 3-4 pairs most produced. Ventral plate pro- 

 duced into a short, rounded lobe. Genitalia: internal part of the an- 

 terior plate not higher than the ventral plate, external part with the 

 tip somewhat rounded, produced backwards and outwards; posterior 

 plate divided at the base, the outer grooved, through which runs the 

 inner, ends of both rounded and more or less roughened. Length of 

 body, 45-100 mm ; width, 5-10 mm . 



Habitat. — Eastern United States. 



I have examined numerous specimens of this species from Bloom- 

 ington, Ind., and one large female from Brooksville, Ind., collected 

 by Mr. Amos Butler. Specimens 50" ,ni long differ in color from the 

 full grown examples, by being dark green. 



Young individuals differ from adults as follows: 



Length. 



Width. 



mm. 

 2 

 o 

 2 

 1 



Segments. 



Pairs of 

 feet. 



Eyes. 



mm. 

 18 



16.5 

 10 



8 



42 

 41 

 39 



27 



It 



65 

 62 

 32 



18-5 

 21-5 

 19-5 

 0-3 



