126 THE AMERICAN MONTHLY (Jun 
median canal is straight, not wavy, as Amphiprora has. 
Abhandlungen, published in 1843, is also dated 1844 
and is known as Amer. The true genus is described by 
T. F. Kutzing in his Baccillarian, 1844, p. 107. He there 
includes A. alata which is Navicula alata 0.G.E. (1840, 
Bor. p. 18). It was found at Cuxhaven, in brackish wa- 
ter, and Kutzing also found, at Trieste, in the Mediter- 
ranean, A. constricta, C.G.E. 1843 (Abhand. p. 122. Taf. 
II, tv, 28) found in the brackish water of Cuba. There 
is a Plagiotropis, A.G. which it will be necessary to con- 
sider as well as an Amphitropis, V.H.,a sub-genus of 
Amphiprora. Amphiprora is defined in the latest book 
we have had on the Bacillaria: Synopsis des Diatome 
de Belgiques, 1880-’81, by Dr. Henri Van Heurck as 
follows: ‘‘Valves boat-shaped, with projecting keels, 
which are straight (Amphiprora) or sigmoid (Amphitro- 
pis). Central and terminal nodules little.”” He gives 
two Amphiprora, A. lepidoptera, W.G. var. pusilla, W. 
G, and A. maxima, W. G.—all from brackish water ex- 
cept that Gregory got them only on dead shells from the 
Firth of Clyde, Scotland. Three sub-genera Amphitro- 
pis alata, C.G.E., A. paludosa, W.S.A. duplex, A.S.D. 
and A. ornata, J. W. B. The first two are marine and 
brackish; the last, fresh-water. ; 
Plagiotropis,H. P. and P. elegans,A.G.—Amphiprora, el- 
egans W.S. and P. van heurckii, A.G., both are marine. 
The form of Plagiotropis is the same as the Amphiprora 
except that the median line is not sigmoid but direct. 
A form is quite common in the fossil condition at Mil- 
burn, N. J., which I cannot see but is Plagiotropis van- 
heurckii. However, it does not agree with the formas 
figured to place it there. It is fresh-water instead of 
marine. It also occurs inthe mud of the Second River, 
N. J., and is the same from the Rahway River, N. J. I 
have not seen it ina living state but it must be common 
in some of those streams, the Rahway, Elizabeth, Pas- 
