58 



spine basally on ventral surface and small basal lobe on inner surface 

 above prefemur; anterior bend moderately sharp, located at nearly 1/3 

 length; peak relatively flat, about 1/4 of acropodite length; apical curve 

 present, broad, located at about 3/4 length; distal zone present, long, 

 curving broadly into arch; tip narrowly rounded, not reflexed, directed 

 toward basal zone. Medial flange arising on basal zone just distal to 

 spine, extending across anterior bend and terminating at midlength of 

 peak, edge curved inward proximally and outward distally, obscurring 

 short section of acropodite stem at anterior bend. Spur absent. Lateral 

 flange present but greatly reduced, forming short rim on distal zone. 

 Prostatic groove running along inner surface of acropodite basally, 

 crossing to lateral side at anterior bend and continuing to tip. 



Male paratypes. — The male paratypes agree essentially with the holo- 

 type in all particulars. 



Female par atype. — Length 48.0 mm, maximum width 11.4mm, W/L 

 ratio 23.8%, depth/ width ratio 67.5%. Agreeing closely with holotype in 

 somatic details except paranota more strongly depressed, creating 

 appearance of more highly arched body. 



Cyphopods in situ with valves visible in aperture, receptacle situated 

 internally against coxae. Receptacle relatively small, located anteriad to 

 and not overlapping valves, surface finely granulate. Valves moderate, 

 inner one slightly larger, surface finely granulate. 



Variation. — Several aspects of the gonopods vary. The size of the 

 spine changes, being generally smaller in material from Abbeville County 

 and greatly reduced in one male from Anderson County. The acropo- 

 dite tends to be thinner and the apical curve broader in the southern 

 specimens, and all males from Abbeville County posses a reflexed tip 

 (Fig. 5). The tip is simple on all other specimens. Specimens from And- 

 erson County have a sharp spine projecting mediad at the base of the 

 medial flange in addition to that at the base of the acropodite, but this 

 structure is absent from the Abbeville County males. All males have an 

 elevated ridge on the prefemur but lack a prefemoral process. 



Ecology. — Brevigonus arcuatus occurs under thin leaf layers on rela- 

 tively hard substrates near rivers or creeks. It is sometimes found on the 

 vertical bank of streams and has rarely been taken more than 6 to 9 m 

 from a water source. 



Distribution. — Piedmont Plateau physiographic province of central- 

 western South Carolina, from southeastern Pickens to southwestern 

 Abbeville counties. Specimens examined as follows (all collected by the 

 author unless otherwise stated): 



SOUTH CAROLINA: Oconee Co.— Clemson vie, under dead 

 pig, 2M, F, 18 July 1962, J. A. Payne (RLH). Pickens Co.— 13.6 km. 

 (8.5 mi.) E Pickens, along SC hwy. 192 at George's Cr., 3M, 2F, 8 May 

 1977 (NCSM A 1559); 7M, F, 2 August 1977 (NCSM A1617); and 5M, 

 2F, 12 June 1978, R. M. Shelley and W. B. Jones (NCSM A2075) 



