SOME DESMIDS OF THE UNITED STATES. 299 
Hab. Laconia, N.H. (H. J. no. 660). 
There is no doubt that Johnson has observed the same plant 
that we doubtfully placed as a form of X. antilopeum. All the 
specimens seen by him had only single spines at the angles, 
whereas many of our examples had a pair of spines at one or 
more of the angles. It is a much smaller species than X. anti- 
lopæum, and although the form of the semicells is about the 
same, yet the spines have the same direction as the paired spines 
of X. cristatum; moreover X. antilopeum never has single spines 
at its angles. ‘The forms of this species may be regarded as 
intermediate between X. inchoatum, Nordst., and X. antilopeum. 
71. XANTHIDIUM HaASTIFERUM, W. B. Turn. in Journ. Hoy. 
Mier. Soc. 1885, p. 938, t. 15. f. 20.—X. antilopoeum var. angu- 
latum, Josh. in Journ. Linn. Soc., Bot. xxi. (1886) p. 643, t. 24. 
f. 16.—X. angulatum, Lagerh. (1887). 
Var. JOHNSONIT, n. var. 
X. antilopeum, forma javanicum, Johnson, Bull. Torr. Bot. 
Club, xxii. (1895), no. 7. p. 295, pl. 239. f. 10; non X. antilo- 
pewn forma javanica, Nordst. 1880 (= X. hastiferum var. 
javanicum, W. B. Turn. 1892). 
Var. spinis brevioribus et quasi uniformibus, spinis apicalibus 
singulis vel geminatis ; serie curvata granulorum 8 infra apicem 
semicellularum. 
Long. e. spin. 644, s. spin. 52; lat. c. spin, 80 p, s. spin. 
32 u; lat. isthm. 124; crass. 30 p. 
Hab. Ann Arbor, Mich. (H. J. no. 324). 
72. X. Jonwsoxri, n. sp. (Pl.17. fig. 1.) 
X. minutissimum, tam longum quam latum (sine spinis), pro- 
funde constrictum, sinu acuto extrorsum ampliato ; semicellule 
hexagono-ellipticm, angulis lateralibus spina longa tenui singula, 
angulis superioribus spinis binis similibus, etiam spinis binis ad 
marginem inferiorem prope basin semicellularum, in centro 
‘pms duabus planitie verticali dispositis; a latere vise sub- 
Circulares, spinis duabus divergentibus prope apicem, spinis 
seminatis divaricatis ad medium utrobique; a vertice vis? 
ellipticæ, spinis tribus divergentibus ad polum unumquemque, 
‘pna singula ad medium utrobique. 
Ong. €. spin. 23 p, s. spin. 1L p; lat. c. spin. 23 p, 8. 8pm- ll p; 
lat. isthm. 53 crass. c. spin. 18 p, s. spin. 6p. 
Hab, Bridgeport, Conn. (H. J. no. 517). 
