736 



SYSTEMATIC HISTORY OF THE INFUSORIA. 



X. (?) Artiscon (Ehr.). — Frond in f. v. 

 about as long as broad ; constriction 

 forming a wide notch ; segments narrowed 

 at the base, with broadly rounded ends ; 

 spines numerous, restricted to the outer 

 margin, scattered, eloncfaie, stout, termi- 

 nated by three or fom* diverging points. 

 — Asteroxantliium Arctiscon (Kg.)* Gr- 



2 * Spines subulate. 



X. acideatum (Ehr.). — Frond in f. v. 

 broader than long; constriction deep, 

 linear ; segments somewhat reniform ; 

 spines subulate, short, scattered, chiejiy 

 marginal ; central protuberance cylin- 

 drical, truncate, border minutely dentate. 

 L. (not including spines) 1-380" ; B. 

 1-1347" to 1-393". = Zygoxanthium 

 acideatum (Kg.). G.B., I., F., Italy, G. 



X. Brebissonii (Ralfs). — Frond in f. v. 

 broader than long ; constriction deep, 

 acute, not linear; segments subelliptic, 

 sometimes irregular ; spines subulate, 

 geminate, marginal ; central protuberance 

 'cylindrical, truncate, border minutely 

 dentate. L. (not including spines) 1 -416" ; 

 B, 1-408" to 1-365". = X. bisenarium 

 (Ehr.), Zygoxanthium aculeatum (Kg.). 

 ^, segments broader and more irregular, 

 spines somewhat irregular and unequal. 

 G.B., I., F., G., U.S.A. 



X. fascieulatum (Ehr.). — Frond about 

 as long as broad ; constriction deep, 

 linear; segments somewhat renifortn or 

 subhexagonal, twice as broad as long ; 

 spines slender, subulate, geminate, mar- 

 ginal, in four or six pairs ; central pro- 

 tuberance short, conical, somewhat trun- 

 cate, a, segts. with four pairs of spines. 

 = X antilopmnn (Br«5b.), X. polygonum 

 (Hass., Breb.). L. (not including spines) 



1-454" to 1-350"; B. 432" to 408". /3, 

 segts. -v^dth six pairs of spines. =X fasci- 

 eulatum, var. polygonum (Ehr.), X fas- 

 cieulatum (Hass., Breb.). L. 1-481" ; 

 B. 1-516". G.B., I., F., G., Italy, U.S.A. 



X. cristatum (Breb.). — Frond rather 

 longer than broad ; constriction deep, 

 linear ; segments subreniform, or truncate 

 at ends ; spines straight or curved, subu- 

 late, marginal, one at each side, at the 

 base of the segment, solitary, the others 

 geminate, in four pairs; central protu- 

 berance short, conical, a, segis. reni- 

 form, spines scarcely cmn^ed. L. (not 

 including spines) 1-357"; B. 1-499". 

 (ii. 18 & 23.) /3, segments truncate at 

 ends, spmes micinate. L. 1-469"; B. 

 1-625". G.B., L, F., U.S.A. 



X. Smithii (Archer). — Frond minute, 

 in f. V. about as long as broad ; constric- 

 tion ^a wide notch ; segments twice as 

 broad as long, trapezoid, lower margin 

 somewhat convex, sides narrowing up- 

 wards and straight, ends broad and 

 straight, angles roimded, each of the four 

 angles presenting a pair of sometvhat 

 divergent, short, minute, acute spines ; s. v. 

 constriction shallow, obtuse ; segments 

 with rounded sides, ends trimcate, each 

 upper angle furnished with a minute spine, 

 beneath each of which, about half way 



all the spines somewhat divergent ; e. v. 

 subelliptic, or broadly fusiform, ends 

 blunt, rounded, furnished with three mi- 

 nute spines, none oi the sides ; central 

 protuberance a minute tubercle, apparent 

 always in this view, but in s. v. some- 

 times hidden by the projecting centi'al 

 spines. L. 1-1166" ; B. 1-1272". G.B. 



Genus AETHRODESMUS (Ehi\).— Frond deeply constricted ; segments 

 compressed, either with four prominent angles and a single or geminate spine, 

 or a tooth, at each angle, or having one spine or acute tooth only, on each side, 

 at each upper or outer extremit}^ ; without a central projection ; e. v. elliptic 

 or fusiform. 



* Segments tvith four prominent angles 

 and a simple or geminate spine, or an 

 acute tooth, at each angle. 



Arthhodesmus octocornis (Ehr., 

 Hass., Breb.). — Frond smooth, minute, 

 about as long as broad; constriction a 

 wide notch ; segments much compressed, 

 trapezoid, each angle terminated by one 

 or two straight, subulate, acute sj^ines, the 

 intervals between the angles concave. 

 a, spine solitarv at each angle. L. 

 1-1351"; B. l-Io38". (i. 30.) ^larger, 



spines geminate at each angle. L. 

 1-1020" ; B. 1-906". (i. 29.) = Micra- 

 sterias octocornis (Menegh., Kg.), Xan- 

 thidium octocorne (Ehr., Ralfs). G.B., 

 I., F., G., Italy, U.S.A. 



A. bijidus (Breb.). — Frond smooth, 

 very minute, about as broad as long: 

 segments soineivhat arcuate, inner margin 

 convex, outer concave, extremities diver- 

 gent, emarginate, each angle terminating 

 in an acute tooth ; e. v. comj)ressed, fusi- 

 form, with a short acute spine or tooth 

 at each end. F. 



