10 NEW SPECIES OF DIATOMACEAE. 



The Oallionella crotonensis constitutes the largest portion of the matter collected by 

 filters from the Croton water in the city of New York, and thousands of its frus- 

 tules must be daily swallowed by those who use the unfiltered water. It is so 

 abundant in the Croton water that it may yet possibly prove of importance as a 

 means of detecting the fraudulent dilution of various substances. A portion of the 

 sediment from a suspected liquid could be taken up with a sucking tube, and then 

 examined with the microscope, when the O. crotonensis, and other characteristic 

 forms, would easily be recognized. (See Article VII.) 



MyalodiiSCEis suMilis, B. 



{Plate, Fig. 12.) 



Discoid, bases with a broad margin, marked like the engine-turned back of a 

 watch, with lines of exceeding delicacy, only visible by the highest magnifiers and 

 careful illumination. Umbilical portion more coarsely granulated, and in size little 

 less than one-third of the diameter of the base. Diameter from 1". to 3". 



Occurs at Halifax, Nova Scotia. 



Ehrenberg's species, H. laevis, resembles the M. svhtilis in many respects, but dif- 

 fers in having a wider margin, covered with much coarser markings. The Halifax 

 specimens, even of the largest size, are so delicately marked as to form admirable 

 test objects for the best microscopic objectives. (See page 14.) 



MyalodlscHs stelliger, B. 



(Not figured.) 



Discoid, bases with a broad margin, covered with distinct rectilinear rows of dots, 

 arranged in sectoral groups, so as to produce a stellate appearance. 



Abundant at St. Augustine, Florida. 



The markings in this species are quite distinct, and the stellate appearance, re- 

 sembling that shown by Goscinodiscus suhtilis, will at once distinguish it from all 

 other species. 



IVavicnIata ^rannlata, 6. 



(Plate, Fig. 16.) 



Bases elliptical, with a smooth longitudinal space reaching from end to end, 

 exterior to which is a coarsely and irregularly granulated portion, bounded by 

 marginal rows of dots or granules. Length, 3™. Width, li™. 



Habitat, Halifax, Nova Scotia. 



Stauroptera ol>long'a, B. 



(Plate, Fig. 17.) 



Lorica, having the size and markings of Stauroptcra asjpera, Ehr., but having its 

 bases oblong, with parallel sides and acute angular ends. 



Found with S. aspera at Halifax, Nova Scotia. For the purpose of comparison, 

 a figure of S. aspera, Ehr., is given. (See Plate, Fig. 18.) 



