M '
Siz e . Length 21 g ; diam, 19 g (A.).
Arclier Micr. Journ. (1860), viii., t. 11, f. 10-12. Rabh.
Alg. Eur. (1868), p. 224.
H ab. In ponds.
Wareham.
Blate X L V,, Jig, 4. a c, living fronds; J d, empty fronds j e, end view;
f , side view.
X a n th id ium Rohin son ian um. Archer inMicr. Journ.{18S0),xx,,
p. 114.
Small, semi-cells trapezoid, the rounded angles crowned by a
few minute spines ; central elevation of the semi-cells bearing a
few irregularly disposed, rather conspicuous granules ; lower
margins straight, isthmus slightly elongated, constriction thus
forming a parallel and straight division between the semi-cells.
Siz e . Not given.
H ab. In pools.
Ireland.
We have not seen this species, which has never been more fully described,
and no figure published.
Gen. 20. ARTHROD ESMUS. plAr. (1836).
Frond deeply constricted; segments compressed, either
with four prominent angles, and a single or geminate spine,
or a tooth, a t each angle, or having one spine or acute tooth
only, on each side, a t each upper or outer ex trem ity ; without
a central projection; end view elliptic or fusiform.
Azthzodesmus oc to co zn is. Ehr. Infus. (1838), p. 152.
Frond smooth, minute, about as long as b ro a d ; constriction
a wide n o tc h ; segments much compressed, trapezoid,
each angle terminated by one or two straight, subulate, acute
spines ; the intervals between the angles concave, zygospore
globose, armed with long simple spines.
S iz e . Diam. 16-25 p (W o .); diam. 16 p (K-).
Archer in P rit. Infus. (1861), pp. 736, t. i., f. 29. Kirchn.
Alg. Schles. 1878), p. 156. Cleve Sver. Desm. (1864),
489. Lnndell Desm. Snec. (1871), p. 55. Nordstedt Norges
Desm. (1873), p. 25. Wood F. Wate r Alg® U.S. (1872),
p. 158. Brebisson Liste Desm. (1856), p. 135. Rabh. Alg.
Eur. (1868), p. 225. Wolle Desm. U.S. (1884), p. 97, t.
24, f. 19-23.
Euastrum octocorne, Kutz. Phy. Germ. (1845), p. 134.
Micrasterias octocornis, Meneg. Syn. Desm. ^ 8 4 0 ), p. 216.
Staurastrum ? octocorne, Ralfs. Ann. Nat. Hist. (1845) xv.,
p. 169, t. 12, f. 3.
Xanthidium octocorne, Ehr. Meterop., t. 1, f. 22. Ralfs.
Desm. (1848), p. 116, t. 20, f. 2. Hassall Pr. Alg. (1845),
Xanthidium octocorne, JacobsenDesm. Denm. (1874),p. 211.
H a b . In ponds.
Sussex, Surrey, Hants, Gloucester, Westmoreland, Cornwall,
Wales ; Prance, Germany, Sweden, Norway, Denmark,
Ita ly , United States.
Plate X L V I I ., fig. 2. a c d, living fronds ; h e, empty fronds ; f ,
side view ; g, end view.
var. a s im p le x . Balfs. Lesm. {184S), p . 116.
Spines solitary a t each angle.
H a b . In ponds, pools, &c.
Cornwall, Westmoreland ; Snssex, Surrey, Hants, North
Wales.
var. ¡i majoz. Balfs. Lesm. (1848), p. 116.
Larger, spines geminate a t each angle.
Rabh. Alg. Eur. (1868), p. 225. Nordstedt Norges Desm.
(1873), p. 25.
H a b . In ponds.
North Wales.
Azthzodesmus in c u s . Hass. F. W. Alg. (1845),p. 357.
Frond minute, smooth, as long as or longer than broad,
constriction a deep sinus; segments with inner margin
tnrgid, outer truncate, spines subulate, acute, zygospore
orbicular, spinuous, spines subulate.
S iz e . Diam. 10-36 p. (Wo.) ; length 22^ p ; diam. 24 p
(K.) ; zygospore, without spines, 22 p (K.).
Ralfs. Desm. (1848), p. 118, t. 20, f. 4. Archer in Prit.
In f (1861), p. 737. Wolle Desm. U.S. (1884), p. 97, t. 24,
f I'-IO. Cleve Sver. Desm. (1864), p. 489. Lnndell Desm.
Suec (1871), p. 54. Nordstedt Norges Desm. (1873), p. 25.
Wittrook Scan. Desm. (1869), p. 15. Breb. Liste Desm.
(1856) p. 135. Wood P. W a te r Alg® U.S. (1872), p. 158.
Rabh. Alg. Eur. (1868), p. 226. Kirchn. Alg. Schles. (1878),
p. 156.
Gosmarium incus, Breh. in Meneg. Syn. Desm. (1840).
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