30 BEITISH FRUISH WATER EHIZOPODA. 



S.-Peterb. Obslich. XXXVI (1906), 2, p. 192; Schou- 

 TEDEN in Ann. Biol. Lacustre, I, 3 (1906), pp. 342, 346 ; 

 Schneider in Arch. Biontol. II, 1 (1908), p. 58. 



Test cliitinous and transparent, elongated, tubular, 

 straight, not compressed, in some examples perceptibly 

 narrowed at the oral extremity ; covered with 

 variously-sized angular, siliceous scales, a ring of 

 smaller ones surrounding the mouth, which either 

 corresponds with the diameter of the test or is slightly 

 dilated. The crown invariably surmounted by a tubular 

 horn, which is more or less curved and deflected at a 

 considerable angle, giving the test, at that part, an 

 unsymmetrical outline. The horn formed of the same 

 chitinous material as the test (in fact, a prolongation of 

 it), and sometimes perforated at the apex. The organ- 

 ism not completely filling the interior of the test ; one or 

 two attachment-threads being visible in the posterior 

 part. Pseudopodia simple and few in number; the 

 nucleus spherical, and, under a high magnification, 

 separated from the plasma, which has numerous round 

 niicleoli embedded in its greyish substance, and one or 

 two contractile vacuoles. 



Dimensions : Length 150 /u, (170 to 200 /.i according 

 to Penard) without the posterior horn. 



In Sphagnum-hogs nearCriccieth and in the Sychnant 

 Pass, North Wales. In Loch Ness, Scotland, at a 

 depth of 300 to 400 feet {D. J. Scourfield). 



This species is rare in Britain. On the Continent, 

 and mainly in the Swiss lakes, according to Penard, 

 it occurs sporadically ; in this country we have met 

 with it very sparingly in wet Spliagnurn. The peculiar 

 horn is practically the only fea'ture which differentiates 

 it from ordinary D. acuminata. The form occurring 

 in Sphagnum most nearly resembles one of Penard's 

 figures in ' Faune Rhiz. Leman ' ; it differs from that 

 figured in ' Les Sarc. des grands Lacs ' in being 

 narrowed below (considerably narrower at the mouth 

 than posteriorly), and from the figure in Penard's 



