296 



BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



TACHIDIUS BREVICORNIS Lilljeborg 



Figure 181 



TacMdius hrevicornis Lilueborg, De crustacei.s ex ordinibus tribus : Cladocera, 

 Ostracoda et Copepoda, in Scania occurrentibu.s, p. 196, pis. 22-24, 1853. — Sars, 

 Crustacea of Norway, vol. 5, p. 328, pis. 218, 219, 1909. 



Occwn^ence. — ^Washed in considerable abundance out of the sand 

 at Buzzards Bay bathing beach, Woods Hole, the sand on the shore 

 of Katama Bay, Marthas Vineyard, and the sand of the surf beach 

 on the south shore of Marthas Vineyard. 



Distribution. — British Isles (Brady) ; Baltic (Lilljeborg) ; coast 

 of France (Canu) ; coast of Norway (Sars) ; Finmark coast (T. 



Scott) ; Adriatic (Car, Ca- 

 razzi, Pesta) ; Arctic Ocean 

 (Willey) ; fresh- water pools, 

 England (Gurney) ; Long 

 Island Sound, N. Y. 

 (Sharpe) ; Charlestown Pond, 

 R. L (Williams); Woods 

 Hole Harbor (Fish). 



Color. — Body transparent 

 with a decided whitish tinge, 

 slightly colored irregularly 

 with yellow and orange 

 blotches ; eye red ; eggs yellow. 

 Female. — Body short and 

 stout, metasome considerably 

 depressed ; urosome tapered 

 posteriorly, not half the 

 length of the metasome, its 

 segments fringed along their 

 posterior margins with spi- 

 nules; caudal rami as wide as 

 long, squarely truncated at the tip, apical seta half the length of the 

 body. Basal segment of first antenna the largest, but not cut on its 

 posterior margin; exopod of second antenna 2-segmented, basal seg- 

 ment with one seta, distal segment with two setae. Endopod of first 

 legs longer than exopod, of the three following pairs of legs shorter, 

 its distal segment in all four pairs with five setae. Each fifth leg a 

 subquadrangular lamina with nine marginal setae, the first and fourth 

 outer ones filiform, the fifth and seventh elongated. Total length, 

 0.5-0.7 mm. 



Male. — Considerably smaller than the female, with a narrower 

 urosome ; the first antennae enlarged and subchelif orm, the first seg- 



FiGUHE 181. — Tachidius hrevicornis: a. Female, 

 dorsal ; h, female, fifth legs ; c, male, fifth 

 and sixth legs 



