COPEPODS OF THE WOODS HOLE REGION" 99 



Female. — Head fused with first segment; fiftli segment rounded 

 at posterior corners and armed with a single spine on either side; 

 genital segment considerably dilated ventrally, with a pointed proc- 

 ess on each lateral margin nearer the base; first abdominal segment 

 only one-seventh as long as anal segment; caudal rami fringed with 

 hairs on both margins; spines on first basipods of fifth legs project- 

 ing beyond the lateral margins ; setae on second basipods fairly long 

 and stout; endopod longer than basal segment of exopod, setose on 

 inner margin distally, with 2 equal apical spines; hook of second 

 exopod segment setose on inner margin; spines representing third 

 segment subequal, the inner 

 one a little the longer. Total 

 length, 1.2-1.4 mm. 



Male. — Grasping antenna 

 much swollen; antepenultimate 

 segment with a blunt process at 

 its outer distal corner; basal 

 segment of right fifth exopod 

 wider than long, with a broad, 

 rectangular hyaline process on 



its inner maro'in * di<^tal sec- figure 66. — Biaptomus Mrgei: a, Female, 

 *= '. " *=>' fifth legs; b, male, fifth legs 



ment enlarged at its base, the 



outer spine long and stout and nearer the base and serrulate on its 

 inner margin, the terminal claw as long as the entire leg, strongly 

 curved and denticulate on the inner margin; endopods of both legs 

 conical, 1-segmented, and longer than the basal segments of the 

 exopods; left exopod tipped with a fingerlike process and a falci- 

 form spine. Total length, 1.1-1.25 mm. 



Remarks. — The fifth legs furnish the best identification for the 

 species. It is evidently well distributed in the small ponds along 

 the eastern shore of Buzzards Bay in the towns of Falmouth and 

 Bourne. When placed in a preservative both sexes wind their anten- 

 nae around the body spirally and distort the urosome in various 

 directions, making them very difficult to examine. 



DIAPTOMUS OREGONENSIS Lilljeborg 



Figure 67 



Diaptomu,s oregonensis Lilljeboeg, M6m. Soc. Zool. France, vol. 2, p. 53, pis. 

 2, 3, 18S9.— Marsh, Trans. Wisconsin Acad. Sci., vol. 15, p. 409, pi. 15, 1907. 



Occurrence. — Both sexes very abundant in Bournes Pond, Fal- 

 mouth ; Great Pond or Chequaket Lake, Barnstable ; Shallow Pond, 

 Barnstable; Seymour or Bangs Pond, Brewster; Crockers Pond, 

 Falmouth; Ice Pond, Quisset, Falmouth; Jones Pond, Waquoit, Fal- 

 mouth; Long Pond, Brewster; Hinckleys Pond, Harwich; Jenkins 

 Pond, Falmouth; less abundant in Crescent Lake, Centerville, Barn- 



