KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 26. N:0 2. 13 



noticed thiw species iii deposits from Warnemiuide in Gerraany and from tlie eaytern Småland 

 in Svveden. 



The microscopical examination of tlie pi'se- and inter-glacial deposits of northern Germany 

 and Denraark have furnislied evidence tliat these strata were formed in inlets from tlie North Sea 

 and not from the Aretic Sea. 



All these facts prove of what importance the stndy of fossil diatomaceaj is becoming to 

 Geologists. 



Ampliiprora Ehb. (1843). 



Valve lanceolate, acute, convex. Axial part of tlie valve elevated into a sigmoid keel, nsually 

 separated from the lower part by a line of jnnction. Axial area indistinct. Central area small 

 or none. Structure of the lower part of the valve: transverse stritE, rarely scattered pnncta- 

 structure of the keel: puncta in transverse or decnssating rows. — Frnstnle strongly constricted 

 in the middle. Jnnction between the keel and the lower part of the valve nsually visible as a 

 more or less sinuose line. Connecting zone complex, with more or less numerons, transversely 

 striate divisions. — Cell-contents (of A. alata) a single cliromotophore-plate along the zone. The 

 division of the chromotophore begins from its ends (Pfitzbr, Bau xi. Entw. p. 94). 



The name Amphiprora was given by Eurenberg 1843 (Am. p. 122) to two uavieuloid dia- 

 toms. Ä. coii.^itricfa, the fignre of whieh represents some species of Navicnla in the frustnlar view, 

 is slightly constricted in the middle. It seems impossible now to make out what form this name 

 may denote. The other Amphiprora is, as the figures in »the Microgeology» shews, Nav. Semen. In 

 the »Bacillarien» Kctzixg adds a third species, A. aJata, which is distingnished by its sigmoid me- 

 dian line, and the lines on both sides of the median line, as well as by a complex connecting zone. 

 Låter on several other forms were described ass Amphiprora by Bailey, W. Smith, and others. 

 "W. Smith describes as Ampliiprora viirca a form with straiglit median line and not complex con- 

 necting zone. Forms of very heterogenons natnre were thus thrown together in the genus Amphi- 

 prora. Rabenhorst tried 1864, (Fl. Eur. Alg. p. 257) to separate the forms with a sigmoid median 

 line as a new genus, Ampliicampa, which name Pfitzer 1871 (Bau und Entw. p. 94) changed to 

 Ampliitropis. — I consider that the name Ampliiprora may be retained for the forms with sigmoid 

 keel and complex zone, as A. alata is the first recognizable form described. For the other forms 

 I have 1891 (Diatomiste I, p. 51) proposed the name Tropidoucis. 



The genus Amphiprora seems to be akin to the Nitzschieaj, and is on the other hand eon- 

 nected with Auricula. The complex zone, the single chromatophore, the pnncta or lines on the keel 

 remind one of the Nitzschiete. In most species of Amphiprora the keel forms a well marked pax't of 

 the valve, bordered by a junction-line, which is frequently denticulated or sinuose, and very sug- 

 gestive of the alse of SurirelhB. Whether this line projects into a true wing, I have not been 

 able to discover. In all cases it occupies the same position as the wing of Surirellse. 



The structure of the valve is somewhat difFerent in different sections. Three types may be 

 distingnished: the type of A. alata, of A. giyantea, and of A. Temi^erci. In the first named the 

 keel as well as the valve have transverse striae. In larger forms of that type the striee seem to 

 be finely transversely lineate, with rather coarser pnncta on the keel, which pnncta appear to be- 

 long to an interiör stratnm. In the forms, of which A. (jigantea is the type, the keel and the 

 lower part of the valve have entirely different structure. The keel has puncta, disposed in obliquely 

 decnssating rows as in Plenrosigma, and the lower part of the valve has transverse strire. In 

 A. Teniperei the keel has two rows of large stigmas and in addition very fine transverse strice, 

 while the lower part of the valve shews only fine scattered puncta. 



Some few forms of Amphiprora live in fresh water, the greater part in brackish water, and 

 some are purely marine. They occur in all parts of the world. 



