270 MR. W. WEST ON SOME FRESHWATER 
ference being in the branches not being aggregate. The hetero- 
cysts vary from subquadrate to subrotund, and are rather 
numerous. 
19. ScyToNEMA AMPLUM, nov. sp. (Pl. XVI. figs. 14-16.) 
8. strato parvo, pannoso, 8-5 mm. lato, fusco ; filis dense in- 
tricatis ; pseudoramis sparsis plerumque geminatis sed interdum 
singulis, filo primario tenuioribus; vaginis amplissimis stratis 
parallelis formatis, in parte exteriore gelatinoso-achrois vel sub- 
luteolis, in parte interiore abrupte luteo-fuscis ; trichomatibus 
angustis, luteo-viridibus, ad apicem pseudo-ramulorum crassior- 
ibus et articulis brevioribus; articulis diametro 33—-Gplo (ple- 
rumque 4plo) longioribus; heterocystis oblongis, diametro 3-33 plo 
(rarius 2plo) longioribus. 
Crass. fil. prim. 19-24 »; crass. ramul. 13°5-16 ; crass. trich. 
35-4 p. 
Hab. On trees, summit of Trois Pitons (4500 ft.), Dominica. 
Nos. 903 and 904.—Growing about and upon the surface of 
Symploca cuspidata, n. sp. 
The nearest species to this with regard to the comparative 
length and breadth of the cells is S. ambiguum, Kuetz., from 
which it differs in its much larger size, stouter habit, compa- 
ratively broader sheath, and in the more unfrequent branches. 
The branches are usually geminate though not unfrequently 
single, and they are always thinner than the primary filament. 
The trichomes at the apices of the branches become almost 
twice as thick, the cells becoming very much shorter. SS. myo- 
chrous, Ag., is somewhat similar though larger, and has not 
such a comparatively broad sheath, and the latter is ocreate. 
20. S. amBreutm, Kuetz. (Species Algarum, p. 894; Tabule 
phycolog. ii. p. 7, t. 26. f. ii.) (PL. XV. figs. 11-15.) 
Crass. fil. 95-115 w; crass. trich. 2-2°5 p. 
Hab. On trees, summit of Trois Pitons (4500 ft.), Dominica. 
No. 903.—On the ground, mostly in old Diablotia holes, Morne 
Anglais (2300 ft.) (15-7-92.) No. 493. Amongst Symploca. 
The figure given by Kuetzing (J. ¢.) is very indistinct ; but the 
specimens agreed well with the description given by Bornet and 
Flahault (Révis. des Nostoc. Hétérocyst. p. 100), excepting that 
the filaments were a little thicker (9°5-11°5 p against 6-9 ,). 
The trichomes were, however, the same. One of its chief 
characters is its long and narrow cells, which get shorter 
aud thicker (up to 3'8,) towards the apices of ‘the young 
