Edwards, on Diatomacem. 
85 
New York State. Fishkill Creek is a tributary of the Hudson 
River, and is about sixty- five miles from the Atlantic Ocean, 
and at the head of tidal influence. The gathering was a 
gray-coloured mud, and is very rich in Diatomacese, though 
the species are few. 
riSHKILL CREEK. 
Amphiprora lepidoptera. Gomphonema dichotomum. 
Cocconeis placentula. Melosira varians. 
Cocconema cistula. Navicula rhomboides. 
Coscinodiscus subtilis. Nitzschia sigmoidea. 
Cyclotella Kiitzingiana. Pinnularia radiosa. 
Cymatopleura elliptica. Surirella linearis. 
solea. „ minuta 
Encyonema prostratum. spleudida. 
Epithemia turgida, Synedra ulna. 
Gomphonema cristatum. Tabellaria flocculosa. 
„ consirictum. 
Two other species occur at this locality, but I have not 
included them in the above list, as but a few specimens were 
found, and one of these is doubtful. They are Tryblionella 
scutellum of Smith, which is synonymous with Surirella cir- 
cumsuta of Bailey, and Navicula peruviana of Ehrenberg, 
and an Actinoptychus, which, in my opinion, is a species of 
Coscinodiscus J as I shall show hereafter. 
HUDSON RIYER. 
Mud taken from the rocks on the shore of the Hudson 
Eiver, at New York Island, about four miles from the Atlantic 
Ocean, yielded the following : 
Achnanthes subsessilis, Melosira nummuloides, and Surirella 
splendida in a living state, and dead frustules of the fol- 
lowing : 
Actinocyclus undulatus. Grammatophora marina. 
Amphiprora lepidoptera. Triceratium favus, 
Amphipleura sigmoidea. „ alternans. 
Coscinodiscus oculus-iridis. 
I found in this gathering a frustule exhibiting the abnormal 
development mentioned by Smith as occurring in Achnanthes 
subsessiliSj and of which he has given a figure. (PI. xxxviii, 
302^.) 
Triceratium alternans of Bailey is found having three 
varieties of outline, the normal form seeming to be that 
having the sides straight, whilst the others are — 
a. With the sides decidedly concave. 
j3. With the sides slightly convex. 
I have found all three varieties together in some gatherings, 
and thus have been able to compare them. 
