TRINBMA COMPLANATUM. 95 



silicious plates ; in broad view of nearly equal width 

 with semicircular extremities; in narrow side view 

 tapering sharply towards the aperture ; transverse 

 section oval ; aperture circular, oblique, invaginated ; 

 plasma colourless, containing many bright granules, 

 partly filling the test ; nucleus large, with one large, 

 or two to three small, nucleoles, placed posteriorly ; 

 pseudopodia few, long, attenuate, rarely branched. 



Length 25-60 /a; breadth 14-40 /x; aperture 6-5- 

 16 fjL ; thickness 12-30 /u, ; nucleus 6-12 //, in diameter. 



Habitat. — Mosses and sphagnum. 



England. — G-enerally distributed. 



Wales. — Frequent in North "Wales. 



Scotland. — St. Kilda (Brown), Outer Hebrides; 

 Inverness-shire, Elginshire, Aberdeenshire, Perthshire, 

 Isle of May (Fifeshire), Argyllshire, Ayrshire, and 

 Wigtownshire (Brown). 



Ireland. — Armagh ; Mayo and the islands off Clew 

 Bay; Galway; Wicklow (Soph.). 



This is the least common of the species belonging 

 to this genus ; although it is to be found in sphagniim, 

 it is more numerous and generally distributed in 

 mosses. It is often seen alive but its pseudopodia are 

 rarely observed ; they are usually two in number, are 

 frequently very long, up to twice or three times the 

 length of the test, and active; occasionally they 

 display short branches. 



It rather closely resembles Trinema enchelys var. 

 galeata, from which it is distinguished by its outline 

 in oral view and the absence of the curved lines 

 running from the aperture to the sides of the test. 



It is also so nearly like Ehrenberg's Arcella nidus- 

 pendidus, the test of which is the same in shape and 

 has imbricated scalesj that they may possibly be the 

 same species. Ehrenberg's description is not, however, 

 sufficiently full to enable us to be certain of the 

 identity. His species is undoubtedly a Trinema, and 

 at least very nearly allied to T. complanatum. 



