604 Annals of the Smith African Museum. 



end are a number (about 12) of weak longitudinal ribs (Fig. 43, A) ; 

 these ribs are not arranged quite symmetrically, being placed at 

 slightly variable distances from one another. They do not extend for 

 the whole length of the testa, but die out at about the middle of its 

 length (Fig. 43, G), being therefore altogether invisible in an indi- 

 vidual viewed from the posterior end (Fig. 43, B). Between the ribs, 

 and over the whole of the rest of the surface of the testa, a very fine 

 pitting can be made out with difficulty (Fig. 43, A, B). This appears 

 to be due to the fact that the pitting is confined to the inner part of 

 the wall of the testa, which presents a slightly interrupted appearance, 

 like that of a pitted membrane, when seen in optical section (Fig. 43, 

 D). The collar is a mere thickening of the edge of the flagellum, 

 aperture and projects very slightly, both on the outer and the inner 

 side (Fig. 43, D). 



In one specimen (Fig. 43, 0) a coarse flagellum, a little longer than 

 the testa, was observed, but apart from that no details of cell-structure 

 could be deciphered. 



3. Trachelomonas oblonga, Lemmermann, op. cit., p. 147, fig. 278. 

 (Fig. 43, E.) 



Samples 12, 14, 15. 



Long., 14-16 ji ; lat., 11-14 /a. Some of the individuals were not 

 nearly as oblong as others, and it seemed that there might be all 

 transitions from this species to a typical T. volvocina. The tests also 

 varied very much in colour, showing all shades from almost colourless, 

 through light brown, to a very deep brown. 



4. Trachelomonas incerta, Lemmermann, op. cit.. p. 151, fig. 284. 

 Var. minor, nov. var. (Fig. 43, G.) 



Differt a typo testis multo minoribus, parte anteriore fere truncata < 

 lateribus superne subparallelis, inferne convergentibus, polo posteriore 

 rotundato. 



Long., 11 fx : lat. max., 7 /x. 



Sample 14. 



This comes very close to the var. truncata of T. oblonga, but the 

 general shape of the testa, tapering as it does towards the back end, is 

 more like that of T. incerta. Lemmermann has already described a 

 small variety of T. incerta, but that is characterised by having a 

 punctate testa. 



5. Trachelomonas hispida (Perty), Stein ; Lemmermann, op. cit,. 

 p. 149, fig. 272. 



Forma typica. 

 Samples 4, 14, 15. 24 



