LEWIS, OX DIATOMACEiE. 161 



broken valves it seems more probable to me that they form 

 supplementary plates, arising from the ala at or near its junc- 

 tion "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 frustulcs present a good 

 deal of the rcctangularity of that species, but in other respects 

 widely differ from it. 



8. Navicula marg'mata, 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; strise 

 moniliform, distinct, about 28 in '001 . Margin of valve bor- 

 dered 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. 



The only two specimens of this beautiful diatom yet found 

 by me were derived, the one from Black Rock Harbour, 

 (Light House Point), on the roots of harbour 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 here- 

 after prove a widely distributed species on the coast, from the 

 fact of its occurrence with recent and fossil at points so re- 

 mote from each other. 



The characteristic ornate border and the peculiar striation 

 serve to distinguish it from any of the panduriform species 

 yet figured or described. 



Hab. — Blue clay, Delaware Eiver (fossil). Light House 

 Point, Black Rock Harbour, on algoe. 



8. Navicula, n. sp.? or sporangium of N. rhomboides ? or 

 N. fossilis, Ehr. — F. V. linear slightly inflated. Y. 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. 



This large hyaline species occurs in salt and brackish locali- 

 ties. It is found in the St. Mary's River, M^ithin two miles 

 of the ocean, and on the Savannah River, below the city. 

 Triceratium favKS is found living in the same localities. In 

 many of its characters it is nearly allied toiV. rhomboides and 

 crassinervia, more particularly to var. j3 of the first named, 

 and, perhaps, notwithstanding its marine habitat, ought to be 

 regarded as a sporangial variety of one or other of these 

 species. 



