332 Notes on New Species 



circular puncta, but when out of focus giving the margin 

 a beautiful and delicate striated appearance. 



DITYLUM, Bail., nov. gen. 



Siliciou3, free, simple, one-celled, bivalve, consisting of 

 two triangular pyramids applied base to base ; vertices of 

 one or both pyramids terminating in acute spines. 



Figs. 6, 10, 11. DiTYLUM TRiGONUM, Bail., nov. sp. 

 Two nearly equal triangular pyramids, applied base to 

 base ; base of each pyramid triangular, with the angles 

 rounded; vertex of each pyramid terminating in an acute 

 spine ; valves punctate, in radiant interrupted lines ; frus- 

 tules equally bivalve, turgid ; lateral view triangular. 



Hub. San Antonio Bay, Para River, 4 fathoms. 



Figs. 12-14. DiTYLUM iN^ QUALE, Bail., nov. sp. Dif- 

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

 other side less turgid, and rising considerably within the 

 margin ; punctate all over. 



Hab. San Antonio Bay. 



Of this curious genus, to which the name of Grymaia 

 was first given by its discoverer, two species have been de- 

 tected. They differ chiefly in the inequality of the valves. 

 In the side view of D. trigonum, when the spine appears 

 as if reduced to a dot, the form very nearly resembles the 

 same view of Triceratium alternans, B. Both species bear 

 some resemblance to some forms of Chcetoceros and Di- 

 cladia. 



Fig. 7. Melosira granulata, L. W. B., nov. sp. Slen- 

 der ; joints cylindrical and punctate in parallel rows ; joints 

 separated by narrow bands devoid of strise, all closely con- 

 nected ; end of filament armed with (6) spines of greater 

 length than the narrow bands ; joints longer than broad, 

 closely binately conjoined. 



Hab. Para River. 



I have detected several filaments and detached frustules 



