163 



ing in a bar across tlie centre of the valve ; valves in front view 

 gibbous at the centre ; outer portions canoe-sbaped ; aspect hyaline ; 

 terminal nodules distinct. 

 Habitat. Para Kiver. 



AMPHITETRA8 CUSPIDATA, Bail., nOV. Sp. 



Sides concave ; lateral view quadrangular, with angles produced 

 and rounded ; cellules distinctly hexagonal ; connecting membrane 

 minutely punctate. 



Hab. Para River. 



DiTYLUM, Bail., nov. gen. 



Siliceous, free, simple, one-celled, bivalve ; consisting of two trian- 

 gular pyramids, applied base to base. Vertices of one or both pyra- 

 mids terminating in acute spines. 



DiTYLUM TRiGONUM, Bail., nov. sp. 



Two, nearly equal, triangular pjTamids, applied base to base ; base 

 of each pyi'amid triangular, with rounded angles. Vertex of each 

 pyramid terminating in an acute spine. Valves punctate in radiant, 

 interrupted lines. Frustules equally bivalve ; turgid ; lateral view 

 triangular. 



Hab. San Antonio Bay, Para Kiver ; four fathoms. 



DiTYLUM iN^QUALE, Bail., nov. sp. 



Differs from D. trigonum, B., in having one side turgid, with the 

 other side less turgid, and rising considerably within the margin ; 

 punctate all over. 



Hab. San Antonio Bay. 



Melosira granulata, L. W. B., nov. sp. 



Slender ; joints cylindrical and punctate in parallel rows ; joints 

 separated by narrow bands, devoid of striae, all closely connected. 

 End of filament armed with (six) spines, of greater length than the 

 narrow bands ; joints longer than broad, closely binately conjoined. 



Hab. Para River. 



CosciNODiscus TENUIS, Bail., nov. sp. 

 Shell excessively thin and hyaline, with radiant rows of minute 

 cells, a small central inconspicuous rosette and a radiate margin. 

 Hab. Para River. 



Navicula septenaria, Bail., nov. sp. 



Minute ; in general outline rhombic ; sides undulated, producing 

 seven wide parts and six constrictions ; central nodule and line dis- 

 tinct ; striae wanting or obscure. 



Hab. Para City. 



