16 PROCEEDINGS OP THE ACADEMY OF 



Triploceras gracile, Bailey. ' Staurastrum Lewisii, sp. nov. 



Triploceras verticillatum, Bailey. \ Staurastrum munitum, sp. nov. 



Euastrum ornatiuu, sp. nov. j Closterium angustatum, K. 



Euastrura elegans {B)-^b.), Ketz. \ Closterium juncidum, i?a//s. 



Euastrum Ralfsii, Rabenh. , Closterium striolatum, Elir. 



Euastrum multilobatum, sp. nov. \ Xanthidium armatum, Br^b. 



Cosraarum Brebesonii, Menegh. , Xantliidium, sp. ? 



Cosmarium commissurale, Br4b. I Micrasterias furcata, Ag. 



Cosmariura cucumis, Corda. Arthrodesmus quadridens, n. sp. 



Cosmarium suborbiculare, sp. nov. Peuium digitus [Ehrb.)^ Br4h. 



Staurastrum arachne, Ralfs. Bambusina Brebesonii, K'z. 



Staurastrum paradoxicum, Meyen. i 



The doctor called attention to the fact that whilst in this neighborhood one 

 rai-ely met with a desmid which was provided with large granules or spines ; 

 in this northern collection bj far the majority of the specimens were so pro- 

 vided. Of Cosmarium commissurale, Breb., Dr. W. stated he had only seen a 

 single specimen, and this differed from the typical form in having the sinus 

 very narrow in its outer portion, and in being shorter, but these differences did 

 not seem enough to justify specific separation. Of Closterium anguslaium, also, 

 but one specimen had been found, which agreed very well with the typical 

 forms, except that it was a little narrower, its greatest breadth not being more 

 than 9-12000^^ = -00075^^. 



The desmid which the doctor referred to Euastrum. Ralfsii he stated to differ 

 considerably from the typical form in the jjroportion of the breadth and length. 

 There are also certainly four, if not more, umbonations on the face of each 

 half-cell. These are nowhere distinctly spoken of as existing, and Mr. Archer, 

 in Pritchard's Infusoria, states there are none visible in the front view of E. 

 Ralfsii. They are, however, represented in the side view of the original figure, 

 and are said to be very noticeable by Mr. Archer himself, when the desmid is 

 so looked at. In the Saco Lake specimens they are always seen in the front 

 view with great difficulty, and in some cases I failed entirely to demonstrate 

 them, so that they do not afford a good character for the indication of a new 

 species. 



Euastrum multilobatum, sp. nov. 



E. magnum, fere duplo longius quam latum, medio profunde constrictum. et 

 cum siuu modice amplo ; a latere medio ventricosum et duplo biumbonatum, 

 ad verticem dilatatum et emarginatum ; semicellulis a fronte trilobatis, lobis 

 sinus amplissiinis inter se sejunctis; lobi basale distiucte late emarginato, 

 lobo centrale obtuso, lobo polare late leviter sinuato-emarginato; semicellulis 

 a vertice quinque lobulatis; cytiodermate laevi. 



Z'iV/OT.— Long. 57-12000^^ = -00475'^; lat 30-12000^^= -0025. 



E. large, about twice as long as broad, in the centre profoundly constricted, 

 with the sinus moderately large ; from the lateral view somewhat enlarged and 

 doubly biurabonate in the middle ; seuiicells from the front trilobate, the lobes 

 separated by very wide sinuses, the basal lobe broadly emarginate, the central 

 lobe obtuse, the end lobe broadly and shallowly sinuately emarginate ; semi- 

 cells from the vertex five lobed ; cytioderm smooth. 



Remarks. — The basal lobes of this beautiful desmid are distinctly five lobu- 

 late, the lateral lobules being longer and broader than the others, which, in- 

 stead of being emarginate, are obtuse. The sinuses separating lobes and lobules 

 are very broad, with very obtuse angles. When the desmid is viewed from 

 two-thirds round, so as to show the anterior and posterior lobules especially, 

 it presents an outline in which all the sinuses are of similar form, and the cen- 

 tral and basal lobes are about equal size ; whereas, when viewed from the 

 front, the basal lobe is much the broader. When the desmid is viewed from 

 the side it is seen to be enlarged in the centre, and provided with two distinct 

 umbonations each side of the comparatively narrow central sinus. 



