28 



G. 0. SARS. 



[No. 8. 



The tail (fig. 3) is provided with 2 well-marked dorsal pro- 

 cesses, the anterior narrowly conic, whereas the posterior occurs 

 very broad, subtriangular, and furnished at its hinder part 

 with a bunch of delicate hairs. The terminal section is not 

 expanded, — tapering, as is does, evenly toward the apex, which 

 is bluntly rounded, with a somewhat projecting anterior angle 

 bearing the apical claws. The dorsal margin is well-nigh straight, 

 and armed in its exterior part with about 8 pairs of denticles, 

 almost equal in size. The apical claws are gently curved, and 

 want every trace of secondary teeth at the base. The caudal 

 setæ are of moderate length, and distinctly bi-articulate. 



The matrix of the specimen described above contained 4 

 rather large summer-eggs, disposed in pairs, and of a regular 

 oval form. exhibiting also a large central oil-globule. 



The body was semi-transparent, with a faint greenish tinge 

 — the yolk-mass of the eggs of a clear bluish-green. 



Observations. — The movements of the animal were 

 most unusually slow, and somewhat jumping in character, from the 

 abrupt and well-nigh rhythmical strokes of the antennæ. The 

 attitude of the body during these movements was almost vertical, 

 and but very little, if any, locomotion was effected, the strokes 

 of the antennæ serving, it would seem, merely to keep the animal 

 suspended in the water. I watched the same specimen for some 

 days together, and was always sure to find it precisely in the 

 same place in the aquary, — about the middle of the water. 



Only a single specimen of this pretty little species was 

 raised from the mud. It made its appearance in one of my 

 aquaries in the first days of June, and at first was so very small 

 as scarcely to be visible save with the aid of a strong magnifier. 

 Soon, however, it increased in size, and after some days became 

 full-grown and ovigerous, whereupon 'the specimen was submitted 

 to a careful microscopic examination and then preserved in 

 spirit. To the best of my judgment, the small ephippium figured 

 in Pl. 1, fig. 13 belongs to this species, its dimensions being 

 exactly such as would agree with the size of the specimen 

 described above. 



