112 BRITISH rEESHWATER EHIZOPODA. 



these aggregations of diatoms are held together by the 

 transparent cuticles of Lecythmm graiiulatum, the 

 enclosed plasma having decayed away or even being- 

 still present and living but escaping observation {vide 

 PI. XLIV, fig. 11); he also raises the question as to 

 whether the diatoms live in symbiotic relationship with 

 the Leci/thium or are retained in a living state to serve 

 as food as need may arise. 



Both conjugation and longitudinal division have been 

 observed to take place in this species. 



L. avidiim Leidy is very similar and may be a large 

 form or variety of this species, it measures 148-220 ju, 

 in length. L. crirvum Leidy appears to be identical 

 with this species. 



4. Lecythium spinosum (Penard) Hopk. 

 (Plate L, figs. 3-6.) 



Trinema spinosum 

 Penard in Mem. Soc. Geneve, XXXI, i, ii (1890), pp. 186-187, pi. x, 

 fe. 72-74. 

 Pamphagus armatus 



Lautbeboen in Zool. Anzieg. XXIX (1901), p. 54 ; in Zeits. wiss. 



Zool. XO (1908), p. 647, pi. xli, f. 3. 

 Penakd (.?= Trinema spinosum) Faune Rhiz. Leman (1902), pp.577— 



678, f. 12 (p. 572). 

 ScHOUTBDEN in Ann. Biol, lacustre, I (1906), pp. 360, 361. 



Test membranous, ovoid or pyriform, unsymme- 

 trically compressed, furnished with short curved 

 spines ; aperture sub-terminal, oblique ; nucleus gran- 

 ular, placed posteriorly ; plasma filling the test, pseudo- 

 podia numerous, simple or branched. 



Length 46-70 /x.; breadth about half the length. 



Habitat. — Aquatic vegetation. Rare. 



England. — Wansted Park, Bpping Porest, Essex 



(Scourfield). 



The figu^res on Plate L are from sketches supplied by 

 Mr. Scourfield, who adds the following description : — 

 " Tests armed with spines, the contents yellowish- 

 green with highly-refringent globules ; pseudopodia 



