NATURAL SCIENCES OF PHILADELPHIA. 17 



EUASTRUM ORNATTTM, Sp. nOV. 



E. oblongum, diametro duplo longius, profunde constrictum, sinu angusto 

 lineari ; seinicellulis a fronte trilobatis; lobis basalibus latissimis, nonnihil 

 sinuato-emarginatis, angulis plus minus productis et rotiindatis ; lobo polare 

 medio profunde lineare inciso, segmentis late rotundalis ; semicellulis a latere 

 bilobatis, lobis basalibus profunde emargiuatis et cum angulis plus minus 

 acutis ; cjtiodermate distincte ordinatim punctato. 



Z>jam.— 35-12000^^= -00029. 



E. oblong, twice as long as broad, profoundly constricted ; semicells from 

 the front trilobate; basal lobe very broad, slightly sinuately-emarginate, 

 angles more or less produced and rounded ; polar lobe medianly profoundly 

 linearly incised, segments broadly rounded ; semicells bilobate at the sides, 

 basal lobes profoundly emarginate and with the angles more or less acute : 

 cytioderme distinctly regular punctate. 



Remarks. — This species is close to E. crassum, from which it differs in the 

 proportionate length, being only twice instead of three times as long as broad : 

 in the size being only three-fourths as large ; and especially in the peculiar 

 lateral splitting, as it were, of the basal lobes. 



Arthrodesmus quadridens, sp. nov. 



A. late ovali, vel suborbicularis, paulum longius quam latum, cum mar- 

 gine crenato-undulato : semicellulis nonnihil reniformibus, utroque fine aculeo 

 subulate, modice robusto, acuto, recurvo, armatis ; cytiodermate cum verrucu- 

 lis paucibus modice minutis in seriebus paucibus dispositis instructo ; semi- 

 cellulis a vertice acute ellipticis, et cum margine crenatp et superficie sparse 

 verruculosa. 



i?iam.—Lat. 3-4000^^ = -00075; long. 5-4000 = -00125^'. 



Broadly oval or suborbicular, a little longer than broad, with the margin 

 crenately undulate; semicells somewhat reuiform, at each end armed with a 

 subulate, moderately robust, acute, recurved large spine ; cytioderm with a 

 few smallish tubercles arranged in three or four rows ; semicells from the ver- 

 tex acutely elliptical, with the margin crenate and the surface sparsely warty. 



Remarks. — This species approximates A. divergens.^ from which it differs in 

 the arrangement of its granules, its attaining not one-half the size, and, I be- 

 lieve, in the larger and more robust spines. 



Staurastrum mcnitum, sp. nov. 



S. submagnum, fere \ plo longius quam latum, medio leviter constrictum : 

 semicellulis a fronte enormiter hexagonis, angulis in processus rectis et diver- 

 gentibus productis, dorso processibus similibus 4 — 5 instructo ; semicellulis 

 a fronte polygonis vel suborbicularibus, margine processibus numerosis, ple- 

 rumque 9 instructo ; dorso processibus 5 — 8 instructis ; processibus omnibus 

 similibus granulato-deutatis, a.piceachroo simplicibus, bifurcatis vel fissis. 

 25-12000^'' = -002. 



Diam. a vertice cum processibus. — 51-12000'''= -00475. Sine process. 



S. rather large, about one-half longer than broad, slightly constricted in 

 the middle; semicells from the front irregularly hexagonal, the angles pro- 

 longed in straight divergent processes, and the surface furnished with four or 

 five similar ones; semicells from the front polygonal or suborbicular, the 

 margin furnished with numerous i)rocesses, mostly about nine, and also with 

 5 — 8 on the dorsum ; processes all similar, granulate-dentate, their transpa- 

 rent apices simple, bifurcate or torn. 



Remarks. — This species is most closely allied to St. fuscigerum, Br^b., from 

 which it is at once distinguished by the orbicular vertex. The constriction 

 between the semicells is also very different. In St. mumtum it is a gradual, 

 not very deep, hour-glass contraction ; in St. fuscigerum it is very narrow 

 and linear. 



