410 Rev. A. M. Norman on Acantholeberis, Lilljeborg, 



his A. sordida shows such marked points of divergence from the 

 type as to make us doubt whether the genus has been founded 

 on sufficiently good grounds, and whether it should not rather 

 be united with Lathonura, Lilljeborg ( = Pasithea, Koch), and 

 Macrothrix. A. curvirostris and A. sordida are the only known 

 members of the genus, and both these species have now been 

 found in Great Britain. 



Acantholeberis curvirostris (Muller). PI. XI. figs. 1-5. 



Daphne curvirostris, O. F. Muller, Zool. Dan. Prod. p. 200. No. 2403. 

 Daphnia curvirostris, O. F. Muller, Entomostraca, p. 93, pi. 13. f. 1 & 2. 

 Acanthocercus rigidus, Schodler, Arcbiv fur Naturgeschichte, 1846, B. i. 



p. 301, pi. 11 & 12. Lievin, " Die Branchiopoden der Danziger Gegend," 



Neueste Schriften der Naturforschenden Gesellschaft in Danzig, B. iv. 



p. 33, pi. 8. f. 1-5. Leydig, Naturgeschichte der Daphniden, p. 195. 

 Acantholeberis curvirostris, Lilljeborg, De Crust, ex ord. Clad. Ostrac. et 



Copep. p. 52, pi. 4. f. 3-7, & pi. 23. f. 10, 11. 



The carapace is somewhat oblong in form, rather truncate 

 below, and with the hind margin nearly straight, since the ma- 

 trix is but little protuberant in the gravid female. The head 

 does not lean forward, as is usually the case among the Daph- 

 niidee, but is remarkably upright. To the upper point of the 

 beak the anterior antennae (Pi. XI. fig. 2) are attached, and from 

 it they are projected at nearly a right angle. These organs are 

 very large, and strap-shaped; they are slightly serrate on the 

 upper margin, and gradually widen towards the extremity, which 

 is furnished with six or eight cylindrical tentaculifonn filaments. 

 The supplemental eye-spot is situated close behind their bases, 

 and is very small. 



The posterior antennse are long and slender ; their peduncles 

 are not very muscular, are corrugated on the basal half, and bear 

 a few minute spines on the surface towards the distal extremity. 

 The upper and four-jointed branch of these antenna? has* the 

 first articulation very small, the second considerably longer, and 

 furnished with a spine on the upper margin, but no seta ; the 

 third is unprovided with appendages ; the fourth terminates in 

 three two-jointed plumose setse and a spine, which does not equal 

 one-third of the basal portion of the setse in length. The first 

 joint of the lower branch bears an unusually long two-jointed 

 seta of remarkable character, and which, indeed, forms one of 

 the chief features in this interesting Entomostracan. The basal 

 portion of this seta is provided with short cilia on the outer or 

 upper margin, while the inner margin is smooth ; the second 

 portion of the seta (PL XI. fig. 3) has a series of rather distant 

 spines upon the outer margin ; and between these spines a high 

 power of the microscope shows a fringe of short, closely-set cilia. 



