a Genus of Entomostraca new to Great Britain. 411 



The second joint of the lower branch of the posterior antennae 

 bears another seta of great length, which differs, however, in its 

 armature from that of the first joint. This seta is plumose on 

 both margins throughout its entire length ; and between the 

 longer hairs of the outer margin of the distal portion are short 

 closely-set cilia (fig. 4), similar in character to those between the 

 spines of the seta which is attached to the first joint. The third 

 joint ends in three two-jointed plumose cilia and a spine. 



The labrum has a large and conspicuous, much elevated, 

 acutely papilliform process in front. The terminal portion of 

 the abdomen is bordered with a closely-set array of spines, and 

 has the sides, moreover, thickly studded with an admixture of 

 slender spines and hairs. The abdominal setse are long, while 

 the terminal claws (fig. 5) are rather short, a little flattened, 

 and minutely pectinated along the edges. The ventral margin 

 of the carapace is fringed throughout its entire length with 

 plumose setae ; and these setse attain an extraordinary length at 

 the angle formed by the junction of the ventral and posterior 

 margins. 



Acantholeberis curvirostris was discovered last summer by 

 Mr. D. Robertson, in the Isle of Cumbrae in the Firth of Clyde, 

 living in some abundance in a small shallow pond about 12 feet 

 square, which had been eut out of the sandstone rock, and was 

 covered at the bottom with moss and Confervse. Mr. Robertson 

 informs us that though the species seems fond of remaining 

 quietly among the weeds, it nevertheless is tolerably active when 

 swimming, which it effects with a slight jerking motion, often in 

 curves. It has a habit of mounting to the surface of the water, 

 and then allowing itself passively and slowly to sink to the bot- 

 tom, with its antennas spread out on either side. It rarely re- 

 sumes active motion when in its downward course, unless it is 

 disturbed. 



A second locality for the species is Crag Lake, Northumber- 

 land, where it has been met with, during the present spring, by 

 Mr. G. S. Brady. 



Acantholeberis sordida (Lievin). PI. XI. figs. 6-9. 



Acanthocercus sordidus, Lievin, " Die Branch, der Danziger Gegend," 

 Neueste Schriften der naturf. Gesells. in Danzig, B. iv. p. 34, pi. 8. 

 f. 7-12. Fischer, Bull, de la Soc. Imp. des Nat. de Moscou, 1854. 

 Leydig, Naturgeschichte der Daphniden, p. 199. 



Carapace nearly round, widest below, and slightly truncate on 

 the inferior margin, tumid, and having the surface clothed with 

 short hair. Anterior antennas largely developed, long, cylin- 

 drical. Posterior antennse short and stout ; their peduncles 



27* 



