Mineralogy and Geology. 127 
seen, and is at once distinguished from all known species by its numer- 
ous arms or projections, of which those belonging to each principal 
subdivision are not arranged as usual in the general plane of the body, 
but one above another in the plane perpendicular to the broadest surface 
to the individual. These arms much resemble those of Xanthidium 
Arctiscon, Eur., and terminate ina similar manner in three or four 
diverging points. Its size is equal to the largest of the genus. It is 
rather rare in the Catskill Ponds. 
Fig. 1 gives the front view, and fig. 2 an oblique view of the body 
thrown up on edge. 
2. Closterium nodosum, (fig. 3.) Body binary, straight, somewhat 
cylindrical, each half having four prominent nodes. 
Fig. 3. 
This species is a recognized by the deep indentations in its out- 
line, corresponding to the constrictions which separate the transverse 
rows of knot-like projections. The clusters of moving corpuscles are 
near the extremities. When highly magnified, the outline shows some- 
thing resembling minute pubescence. It is one of the largest species 
of the genus. I found vast numbers of this species in the Catskill 
Ponds, all agreeing with the above ew 
Fig. 5. 
3. Closterium verrucosum, (fig. 4.) Body binary, straight, cylindri- 
cal, with numerous transverse rows of small prominences. Moving 
corpuscles near the extremities. This is a pretty species, with a wa- 
ved outline caused by the slight projections, which are arranged in nu- 
merous transverse rings. It is quite abundant with the penton in 
the Catskill Ponds. 
The detection of the above forms gives reason to hope, that ote 
species equally curious may be found when the pene of ——- 
sub-alpine ponds are examined. 
N. B. The figures which accompany this notice are dinewtd 16a, 
scale which is represented by fig. 5. This shows 1°; of a millimetre 
magnified equally with the drawings, which are much less — 
than those given in the plates of the American —— 
