SUBTERRANEAN AMPHIPOD STYGONECTES 47 



antennae, mouth parts, pereopods 3-7, pleopods, abdominal side 

 plates, and iiropod 2. Principal differences between these two groups 

 exist in the structure of gnathopods, uropods 1 and 3, and telson. 



Distribution and ecology. — As presently known, this group is 

 composed of two closely related species and ranges in habitat from 

 shallow, interstitial ground waters of unconsolidated, coastal plain 

 sediments to interstices and crevices in Precambrian crystalline rocks 

 (and probably overlying mantle), and to a lesser extent in caves 

 and solution channels developed in lower Paleozoic bedrock. The 

 pizzinii group occurs from Lancaster and Chester Counties, Pa., 

 south to the vicinity of Washington, D.C., and then again in 

 Nansemond Co., Va. 



Key to Species of the pizzinii Group 



1. Distal notch of 1st gnathopodal propod palmar margin not deeply excavate 

 and prominent only in very large males; distoposterior lobe of pereopod 7 

 basis not much produced ventrally in mature males; telson with up to 2 

 or more sets of lateral spines per side in both sexes; subterranean waters of 

 southeastern Pennsylvania southwestward to the vicinity of metropolitan 



Washington, D.C S. pizzinii (Shoemaker) 



Distal notch rather deeply excavate and prominent in males 8.00 mm and 

 longer; distoposterior lobe of pereopod 7 basis prominent, ventrally pro- 

 duced; telson with fewer lateral spines in both sexes; known only from 2 

 localities in Nansemond Co., Va S. indentatus, new species 



Stygonectes pizzinii (Shoemaker), new combination 



Figure 10 



Synpleonia pizzinii Shoemaker, 1938, pp. 137-142 (in part) [Type locahty: 

 Wetzels Spring, Glover Archbold Parkway, Washington, D.C.]. — Hubricht 

 and Mackin, 1940, pp. 204-205.— Dearolf, 1941, p. 171 (in part).— Shoe- 

 maker, 1942a, pp. 27-31, figs. 10-12 (in part).— Pennak, 1953, p. 443, fig. 

 276a, b.— Barnard, 1958, p. 74.— Hubricht, 1959, p. 878.— Nicholas, 1960, p. 

 130.— Holsinger, 1963, p. 29 (in part) .— Holsinger, 1964, p. 62 (in part). 

 [Not Hubricht, 1943, p. 709.] 



Material examined 



Washington, D.C. — Wetzels Spring, Glover Archbold Parkway, male holotype 

 (USNM 76116), A. Pizzini, Mar. 6, 1932. Additional material as follows (in 

 USNM unless otherwise indicated): Washington, D.C. — Wetzels Spring, 17 

 collections made by A. Pizzini between Aug. 8, 1932, and Dec. 18, 1937; spring in 

 Burleith Woods (also in Glover Archbold Parkway), A. Pizzini, Mar. 8, 1936; 

 Wetzels Spring, J. R. Holsinger and A. Pizzini, May 22, 1965 (JRH). Virginia. — 

 Fairfax Co.: spring at BuUneck Run, A. Pizzini, May 8, 1937; seep between Scott 

 and Bullneck Run, A. Pizzini, Mar. 27, 1938; spring near Scott Run, A. Pizzini, 

 Oct. 24, 1937, and June 14, 1938; well in Virginia (no other data on label), W. 

 Wallace, Oct. 18, 1921. Maryland. — Montgomery Co.: well on Mineshoe 

 Island in Potomac River, C. R. Shoemaker, May 17, 1931; Frederick Co.: 

 artesian well on south side of Sugarloaf Mt., T. Ulke, Apr. 17, 1938; Howard Co.: 

 EUiott City (habitat not given on label), G. N. Ackerman, June 1938. Pennsyl- 

 vania.— Chester Co.: small, walled spring, 1 mile S of New Centerville, L. 



