378 DE8CHIPTI0N OF \^Polygagtrica. 



at last present themselves as tAVO lamellae, separated by an inter- 

 mediate third line. The perforations which Ehrenberg described, 

 I look upon as nothing more than inter- cellular spaces, formed 

 between the two new-formed cells and the parent cell. These so- 

 called perforations are only visible, therefore, on the two lateral 

 borders where the wall abuts upon the membrane. The Confei*void 

 Algae exhibit a similar appearance." 



"Under the name Melosira, Kiitzing describes the following addi- 

 tional species or varieties of GallioneUa. 



Melosiha mimmuloides. — Large, segments with very finely dotted 

 valves, (when dried of a golden colour) ; with evident keels 

 (carinae.) Diameter l-840th. Baltic, North Sea, and Coast of 

 North America. 



The name of this species would suggest its identity with GallioneUa 

 mimmuloides (Ehr.), but Kiitzing finds the synonyme of the latter in 

 his Melosira salina, between which and the Melosira just described, he 

 indicates a specific distinction. 



M. dubia. — Small ; joints compressed spheroids, smooth. Diameter 

 l-1200th. 



M. suhflexilis. — Of middle size ; joints cylindrical, quite smooth ; 

 the younger ones elongated ; the aUult shortened, depressed, conjoined 

 in pairs ; secondary sides rather convex ; connecting isthmus of the 

 conjoined segments short. Diameter l-564th. Friburg. 



M. tenuis. — Very slender; joints cylindrical, quite smooth; long 

 diameter one-and-a-half to two times greater ; closely connate ; no 

 Bulci. Diameter 1-5 760th. Fossil in the polishing powder of 

 Luneberg. 



M. Jurgensii. — Slender ; joints quite smooth, elongate, with two 

 slight contractions beneath the siliceous epidermis ; at junction 

 surfaces convex, hemispherical, closely concatenate. Diameter 

 l-1800th. to l-1200th. 



M. Iletrurica. — Small, joints cylindrical, depth double the width ; 

 margin of junction surfaces finely denticulate ; lateral surface -with 

 dotted rays. Diameter 1 -3600th. to 1-1 800th. Fossil, SanFiore. 



M. Italica. — Small, joints cylindrical, quite smooth ; long diameter 

 (depth) double the transverse (width) ; on secondary sides convex. 

 In the mountain meal of San Fiore. 



