446 DESCRIPTION OF \^Polygastnca. 



Tabellaeia minimwn (Ralfs.) — 'Frustiiles very miuute, about twice 

 as long as broad ; nearly colourless. No striae visible. Found on 

 Conferva, Penzance. 



Genus Teepsinoe. (Ebr.) — Lorica bivalve, compressed, quadran- 

 gular, free ; breadth exceeding the length ; made up of three cells, 

 each cell intersected by two septa, recalling the appearance of bai's 

 of music, each bar presenting also curved bodies resembling notes. 



These large and well marked forms approach nearest to the 

 AMcan genus Tetragramma, which has four septa, and musical, 

 note-like cells, and is nearly as long as broad. Each of these genera 

 exceeds, in size the similarly formed cells of Grammatophora. 



Kiitzing's description rather differs : — 



" Bacilli tabulate, attached, obsoletely stiped, at length parting, 

 and concatenate by an isthmus ; with transverse (not pervious) 

 and capitate vittiB, shortened and marginal ; on secondaiy side nodose. 

 On the upper surface, or face of the quadrangular plates, is a vaulted 

 elevation, extending outwards on each side to the margin; and 

 which is well seen Avhen the lorica lies on one of its narrow sides." 



T. musica. — Lorica two to three times broader than long ; very 

 finely punctated longitudinally, ha-s-ing two transverse smooth bands, 

 more or less apart. (P. 14, f. 47.) In salt and fresh water. Vera 

 Cruz, Mexico. 



Genus Tessella. The flat chain Animalcules. — Filaments free, for 

 though often entangled together, they are never attached ; lorica 

 bivalved or multivalved, prismatic, and expanded so as to have a 

 tabular compressed form. In consequence of perfect self-di\ision of 

 the loinca, and imperfect division of the body, they are developed in 

 the form of gaping chains or zig-zag clusters. In organization they 

 stand between Achnanthes and Bacillaria. Wo opening in the lorica 

 has been distinctly seen ; longitudinal clefts are present, and essen- 

 tially characterize this genus. The ova cluster has numerous lappets, 

 and looks like a great number of round yellowish- green coloured spots, 

 which are not the ova themselves, but the structure containing them. 



The genus Tessella of Kiitzing, a member of the family Striatellece, 

 contains but one species, viz., T. interrupta, the two other forms 

 described by Ehrenberg being placed in other genera, viz., T. arciiata 

 in Striatella, and T. Catena in Rhahdomena. The characters ai'e thus 



