708 PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXXIII. 



iipi^er posterior angle. This species may at once be distinguished 

 from the other two common species, S. vefuhis (O. F. Miiller) and S. 

 expinosus (Koch), by the head, which is decidedly angled below and 

 has many small spines (Plate LIX, fig. 4) . The sculpture of the shell 

 consists of nearly parallel lines (Plate LIX, fig. 5), but anastomosing 

 here and there and in certain parts of the shell making an irregular 

 network. 



This species was found in but one of the lots of material, that col- 

 lected at St. Marys Eiver, Lewis Inlet, Labrador, July 12, 1906. In 

 this lot of material it was fairly well represented. No males were 

 found. The distribution of this species includes Europe and both 

 North and South America. 



Family LYNCODAPHNID^. 



Genus OPHRYOXUS G. O. Sars, 1861. 



OPHRYOXUS GRACILIS G. O. Sars. 



Plate LIX, fig. 6 ; Plate LX, figs. 1-4. 



Ofnjonpus gracilis G. O. Sars, Om de i Omegnen af Christiana forekom- 

 mende Cladocerer, Christiana Videusk, Selsk. Fordhandl., 1861, p. 16. 



Ophryoxus gracilis G. O. Sars, Oversigt af Norges Cnistaceer (Brauchi- 

 opoda, Ostracoda, Cirripedia), Christiana Videusk. Selsk. Forhandl., 

 1S90, No. 1, p. 45. — LiLLJEBORG, Cladocera SueciiB, Nova Acta Reg. See. 

 Sc. Upsala, 3d ser., XIX, 1900, p. 311, pi. li, figs. 0-11 ; pi. lii, figs. 1-10. 



Length of females about 1.80 mm. 



The outline of a female specimen of this species is shown in Plate 

 LX, fig. 1. There is less variation in the outline of this species than 

 in the two previously noted. The pigment fleck is small and close to 

 the insertion of the antennula. The antennula (Plate LIX, fig. 6) is 

 an organ of complicated structure. There is a double row of setae 

 along the proximal half of the inner margin, the distal portion being 

 only slightly spinose, as is the whole of the outer margin. Very near 

 the upper end is the sense seta, longer and somewhat stouter than the 

 setse of the inner margin. Close to this is a large pigment fleck which, 

 in these specimens, seemed to be larger than those usually found in 

 this species. At the distal end of the antennula are three lanceolate 

 projections and several shorter, smaller ones. One point which has 

 not been particularly noted is the peculiar median constriction in the 

 lanceolate spines. This is shown in Plate LIX, fig. 6. 



The post-abdomen (Plate LX, fig. 2) has, besides the strong ter- 

 minal claws, a series of smaller projections. These are not smooth 

 as usually shown but, as may be seen in the enlargement of the fourth 

 projection (Plate LX, fig. 3), are fringed on the posterior border by 

 filamentous projections decreasing in length toward the base. The 

 various appendages have a complicated structure, as may be seen 

 from the figure of the second foot (Plate LX, fig. 4). 



