1 6 American Quarterly Microscopical Journal. 



is quite twisted, and also the variety of Fragilaria capucina, (if 

 it be a variety of this diatom) known as F. Crotonensis, and 

 also some of the Synedrce, Does this, when taken in connection 

 with the occurrence of Rhizosolenia, and an Actinocyclus^ to be 

 described presentl}^ indicate that salt or brackish water is to 

 be found at the bottom of the great Lakes, in which these dia- 

 toms live, or by which they are modified ? It is well known 

 that the late Mr. Stimpson, in connection with Dr. Hoy, of 

 Racine, and others, dredged in some sixty-four fathoms, from 

 the bottom of Lake Michigan, a marine crustacean of the 

 genus My sis, and other forms of a decidedly arctic type; 

 whence it has been inferred that the great Lakes formerly had 

 communication not only with the Atlantic through the St. 

 Lawrence, but with the Arctic Ocean through Hudson's Bay. 

 Although the Rhizosolenieae have been found in tropical waters, 

 they are far more abundant in those of high latitudes. R. 

 Eriensis has never been found as a littoral form, and is only 

 known from filterings of water taken at a great distance from 

 the shore, and from a considerable depth. 



Cestodiscus Baileyi, n. sp. H. L. S. Hab. Lower Lake Klamath. 

 Lt. Williamson. Disc circular, diam. .0025 to .0028, inflated, 

 and with distinct radiating granules ; and showing more or 

 less the characteristic subulate blank spaces of Actinocyclus; 

 without umbilicus; processes intra-marginal, small, and nu- 

 merous ; the punctae near the margin of the valve are in paral- 

 lel rows, 27 in .001. Secondary plate or septum, with a large 

 central opening, fringed with somewhat irregular rays, which 

 do not reach the margin. Plate III, fig. 8. 



This species constituted the larger portion of one of the 

 " Infusorial Marls " from the neighborhood of Lost River, 

 Lower Klamath Lake, Oregon, and was collected by Lt. William- 

 son, as noticed in Volume VI, " Reports of Pacific R. R. Explora- 

 tions." I am not sure that this diatom belongs to Greville's 

 genus Cestodiscus (or even that the genus itself is a good one) ; the 

 intra-marginal processes, not connected by a furrow, or distinct 

 line, would seem to place it here, but it has, on the other hand, 

 many affinities with Melosira. Provisionally, I place it in 

 Greville's genus, and name it after the distinguished micro- 

 scopist from whom I received the material, and whose notice of 

 these infusorial earths was received too late for insertion in 



