^•\t.viculacl^u.] iNFi'soitiAL animalcules. 447 



given — " liacilli broiidly tabular, not concatenate, deuaely ajid lon- 

 gitudinally vittate ; the vdttae interrupted at the middle, and alter- 

 nating: stipes none." 



In assigning it as a character that Tessella docs not form chains or 

 occur as filaments, Kiitzing differs materially both from Ehrenberg 

 and Ralfs, both of whom state the contrary as the case. 



Tessella differs from Striatella, as its filaments are not attached ; 

 from Tetracyclm, as its frustules here and there cohere at their angles ; 

 and from Tahelhria, as its striae are not interrupted at the centre. 

 (Ann. N. H. 1843, p. 104). 



Kiitzing asserts that Mi'. Ealfs has erred in identifying the species 

 described by him as Tessella Catena with that possessing the like name 

 in Ehrenberg' s work. 



Ml". Ealfs writes, " Striatella, Tahellaria, Tetracyclus, and Tessella, 

 form a distinct group of the Cymhellece (Biatomm), distinguished from 

 the other genera by having striae on the central portion of the frus- 

 tule." Again, speaking especially of T. Catena, " From my speci- 

 mens I was unable to ascertain whether the filaments were attached 

 or not, they are fr'agile, and here and there cohere at theii' angles in 

 the same manner as Striatella arcuata .... but, unlike the last, are 

 less fragile, and tui-n green in drying." 



Tessella Catena. — Lorica tabular, often broader than long ; with 

 from 4 to 24 longitudinal series of ti-ausverse striae, and a double row 

 of marginal vittae (seef. 180, 181, and 182), lateral surfaces striated, 

 contracted near the ends. Found on sea weeds. Length of table 

 (that is breadth of the bands) l-570th to l-240th. 



T. arcuata = Striatella unipunctata ^Kiitz.y — Is nearly square 

 and marked with continuous longitudinal lines, but not with trans- 

 verse striae. Kiitzing describes it as having stipes. Length 1 -430th. 



T. internopta. — Is nearly square, with the longitudinal lines inter- 

 rupted in the middle ; striae none. Length of table 1-5 70th. On 

 the English coast, &c. 



Genus Tetkacycltjs. (Ralfs). — Filaments free, attenuated, and 

 forming the segment of a distinct circle ; frustvdes longitudinally 

 striated (Ann. IS". H. v. 12, p. 105). 



T. lacustris. — Frustules (testules, Ehr.), about twice as broad as 



