COPEPODS OF THE WOODS HOLE REGION 213 



Color. — Body yellowish white, irregularly shaded with light 

 brown ; eye dark red. 



Female. — Body much resembling that of the previous species, but 

 shorter and thicker, with the metasome segments more completely 

 telescoped; cephalic segment twee as long as the rest of the body, 

 strongly arched dorsally; genital segment divided; longest seta of 

 caudal rami three times the length of the urosome. First antennae 

 short, but 7-segmented, terminal portion made up of the last three 

 segments; basal expansion of fifth legs almost obsolete, not reaching 

 beyond the base of the distal segment and armed with five short 

 setae ; distal segment small and narrowed at its tip, the apical seta 

 the longest. Total length, 0,3-0.35 mm. 



Male. — First antennae geniculate, the terminal portion containing 

 three segments ; distal segment of second endopod broad and angular, 

 with two apical spines, the inner one wide and sickle-shaped, the outer 

 one very short and triangular ; the spine on the outer margin is also 

 short and triangular; fifth legs like those of the female, the basal 

 expansion reduced to almost nothing and armed with three small 

 setae; distal segment with five setae. Total length, 0.27-0.32 mm. 



Remarks. — This is a dwarf species and may be distinguished by 

 that character and by the reduction of the basal expansion in the 

 fifth legs. It is found in moderate depths among algae, and has not 

 before been reported from our shores. 



Family DIOSACCIDAE 



Genus DIOSACCUS Boeck, 1872 



Metasome strongly compressed ; head fused with the first segment, 

 its epimeral portions extended ventrall}^ to inclose the mouth parts ; 

 rostrum large and prominent; urosome 4-segmented, tapered poste- 

 riorly; genital segment divided; the anterior half inflated laterally. 

 First antennae 8-segmented; exopod of second antennae 1-segmented; 

 first four pairs of legs with 3-segmented rami ; second endopod 2-seg- 

 mented and modified in the male; fifth legs 2-segmented in female, 

 1-segmented in male, the setae partly spiniform. Two ovisacs. One 

 species found here. 



DIOSACCUS TENUICORNIS (Claus) 

 FiGUKE 143 



Dactylopus tenuicorms Claus, Die frei lebenden Copepoden, p. 127, pi. 16, 1863. 

 Diosaccus tenuicorms Sabs, Crustacea of Norway, vol. 5, p. 146, pis. 89, 90, 1906. 



Occui'rence. — Found in small numbers in Eel Pond, Woods Hole; 

 Great Pond, Falmouth ; Katama Bay and Nashaquitsa Pond, Marthas 

 Vineyard; one of the brackish ponds on Chappaquiddick Island. 



