206 BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



with five setae, well separated from one another; distal segment nar- 

 rowed at the tip, with two apical setae of about equal length, three 

 setae on the outer and one on the inner margin. Total length, 

 0.5-0.6 mm. 



Male. — Unknown. 



Remarks. — Brian has published good figures and descriptions ol 

 the nauplius, metanauplius, and copepodid stages of this copepod in 

 Studi del Laboratorio Marino Genova, 1921 (pp. 79-80). The 

 species can be distinguished from the preceding by the structure of 

 the fifth legs and the caudal rami ; like for-fi,cula it has never before 

 been reported from this side of the Atlantic. 



Genus DACTYLOPUSIA Norman, 1903 



Body stout, tapering posteriorly; head fused with the first seg- 

 ment and more or less de^^ressed ; urosome not sharply defined from 

 the metasome, 4-segmented in both sexes; genital segment partly 

 divided; caudal rami much wider than long. First antennae short, 

 the number of segments various; exopod of second antennae 3-seg- 

 mented; first four pairs of legs with 3-segmented rami, endopod of 

 second pair modified in male; fifth legs 2-segmented, broad and 

 lamellar. 



KEY TO THE SPECIES 

 FEMALES 



1. Fifth legs showing: a regular row of short transverse chitin ribs 2 



Neither segment of fifth legs showing any traces of chitin ribs ; 



first antennae very short and stout, 5-segmented brevicornis (p. 206) 



2. A single row of chitin ribs along inner margin of basal expan- 



sion of fifth legs; first antennae 8-segniented tisboides (p. 207) 



Two rows of chitin ribs, one on basal expansion, the other on 

 distal segment, along inner margins ; first antennae 9-seg- 

 mented vulgaris (p. 209) 



MALES 



1. Inner expansion of basal segment of fifth legs removed from, 



and shorter than, distal segment, which is armed with 5 setae 2 



Inner expansion of basal segment of fiftli legs close to, and as 

 long as, distal segment, which is armed with 7 setae vulgaris (p. 209) 



2. Distal segment of second endopod twice as long as wide, with 2 



unequal apical spines and a very stout outer spine tisboides (p. 207) 



Distal segment of second endopod as wide as long, Avith 1 bent 



spine at outer corner and an outer fringe of cilia brevicornis (p. 206) 



DACTYLOPUSIA BREVICORNIS (Glaus) 



Figure 137 



Dactylopus hrevicornis Claus, Die Copepodenfauna von Nizza, p. 29, pi. 3, 1866. 

 Dactylopusia 'brevicornis Sabs, Crustacea of Norway, vol. 5, p. 130, pi. 80, 1905. 



Occurrence. — Found in small numbers in Penzance Pond, Woods 

 Hole, Great Pond, Falmouth, and one of the brackish ponds on 



