64 PROCEEDINGS OP THE ACADEMY OF 



By the central portion of tlie outer aspect or margin of these plates, each frus- 

 tule is united to the adjoining one on both sides, the keels or alae 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 Amphiprora into 

 bands or otherwise. In consequence of this arrangement, an end view of the 

 frustule can readily be obtained. 



Hab. On marine algae (ceramium) off Light House Rocks, New London, 

 abundant. The bands of frustules are often moulded around the smaller stems 

 of Rhodospermeae. 



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, striae 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 algae (Dasya e 1 e g a n s) from a brackish lake at Narragansett. 



This beautiful and delicate little form I have found only at Narragansett. 

 Its very small size, and faint markings make it so inconspicuous an object that a 

 l-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. o r n a t a Bailey, in size and 

 markings. Many of the frustules present a goo 1 deal of the rectangularity of 

 that species, but in other respects widely differ from it. 



8. Navicula m ar g in at a, 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, 

 striae 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, 6 in "001. Length of 

 valve 005 to .006. PI. 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 algae. 



8. Navicula, n. sp. ? or sporangium ofN. rhomboides? orN. fossilis 

 Ehr. F. V. Linear slightly inflaied. V. Lance elliptic, striate ; striae parallel, 

 very clear and sharp, 50 a 60 in "001 ; central line, together with nodules, very 

 prominent. Length of valve -004 to -013. PI. II. 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 f avus is found living in the same localities. In 

 many of its characters it is nearly allied to N. rhomboides and eras- 

 sinervia, more particularly to Var. /?, of the first named, and, perhaps, 

 notwithstanding its marine habitat, ought to be regarded as a sporangia! 

 variety of one or other of these species. 



[March, 



