6 
from its extremity, they are troadly convex and incline somewhat outwards. 
By the central portion of the outer aspect or margin of these plates, each frus- 
tule is united to the adjoining one on both sides, the keels or ale of all three 
overlapping for about one half their breadth A nearly perfect circle is thus 
often formed by a union of from 8 to 12 frustules. I am not aware of any des- 
cription heretofore given of the union of the frustules of Ampbiprora into 
bands or otherwise. In consequence of this arrangement, an end view of the 
frustule can readily be obtained. i 
Hab.—On marine alge (ceramium) off Light House Rocks, New London, 
abundant. The bands of frustules are often moulded around the smaller stems 
of Rhodospermeze. 
7. Amphiprora Nereis, n. sp. Frustule usually twisted, hyaline, very in- 
conspicuous. F. V. Elliptical with rounded ends, constriction of keel or ala 
very deep. V. Striated, strie from 50 a 60 in :001, extending to margin of 
ala. Supplementary plates? crenulate or undulating, at the margin appear- 
ing as though perforated with small puncta. Length of valve -002 a ‘0045. 
Hab.—On alge (Dasya elegans) from a brackish lake at Narragansett. 
This beautiful and delicate little form I have found only at Narragansett. 
Its small size, and faint markings make it so inconspicuous an object that a 
1-12th inch is required not only to define but even to detect the balsamed speci- 
mens on a moderately crowded slide. The only indication of marking arrest- 
ing the eye, is the lines of puncta or dots seen in PI. I. f. 6. These I at first sup- 
posed were portions of the ala, but after examining several specimens and 
fragments of broken valves it seems more probable to me that they form sup- 
plementary plates, arising from the ala at or near its junction with the body 
of the frustule, and occupying the same plane as the former. 
This Amphiprora most nearly resembles A. ornata Bailey, in size and 
markings. Many of the frustules present a good deal of the rectangularity of 
that species, but in other respects widely differ from it. 
8. Naviculamarginata, n.sp. F. V. Oblong, slightly constricted, with 
rounded ends. V. Panduriform, deeply and abruptly constricted. Segments 
lanceolate with subacute extremities. Surface of valve very convex, striate, 
strie moniliform, distinct, about 28 in ‘001. Margin of valve bordered by a 
series of numerous small and beautifully distinct arches, apparently due to 
the absence or depression of the outer silicious plate, 6in ‘001. Length of 
valve 005 to .006. Pl. II. f. 1. 
The only two specimens of this beautiful diatom yet found by me, were 
derived, the one from Black Rock Harbor, (Light House Point,) on the roots 
of harbor grass; the other, an imperfect frustule, from the blue clay of the 
old Delaware estuary, (fossil). The former was a perfect frustule, and has 
furnished the drawings. It is very likely that this will hereafter prove a 
widely distributed species on the coast, from the fact of its occurrence with 
recent and fossil at points so remote from each other. 
The characteristic ornate border and the peculiar striation serve to dis- 
tinguish it from any of the panduriform species yet figured or described. 
Hab.—Blue clay, Delaware river, (fossil). Light House Point, Black Rock 
Harbor. On alge. 
9. Navicula, n. sp.? or sporangium of N. rhomboides?—F. V. Linear 
slightly inflated. V. Lance elliptic, striate; strie parallel, very clear and 
sharp, 50 a 60 in '001; central line, together with nodules, very prominent. 
Length of valve ‘004 to -013. Pl. IL. f. 3. 
This large hyaline species occurs in salt and brackish localities. It is found in 
the St. Mary’s river, within two miles of the ocean, and on the Savannah river, 
below the city. Triceratium favus is found living in the same localities. In 
many of its characters it is nearly allied to N. rhomboides and cras- 
sinervia, more particularly to Var. ~, of the first named, and, perhaps, 
notwithstanding its marine habitat, ought to be regarded as a variety of 
one or other of these species. 
