^6 DESMIDS OF THE U^'ITED STATES. 



center ; central area nude except five or six vertical series of 

 smaller granules : end view shows a prominent central infla- 

 tion ; lateral view broadly ovate, sinuate towards the ends. 

 Diameter 65-70 yu. ; length 90-95 yu. 



Occurs frequently in ponds, northern New Jersey and in 

 Pennsylvania. 



€. Pectinoides, Wolle. Plate XXII. figs. 12. 13. 



Suborbicular, somewhat longer than broad, constriction 

 deep, sinus narrow linear within and widening outwardly; 

 semi- cells semiorbicular with the angles rounded, undulate 

 on the margins with twenty or more crenulations ; rough 

 with geminate rows of pearly granules symmetrically ar- 

 ranged in radiating and concentric lines. On green cells 

 the united twinned granules appear oblong and the crenu- 

 lations dentate ; at the base of the semi- cells the inflation is 

 marked with six, more or less distinct, vertical series of 

 smaller granules ; end and side view evidence a distinct basal 

 protuberance. 



Diameter 45 yu. ; length 60 yU. ; somewhat variable in size. 



A resemblance to forms of many seaside shells suggested 

 the name. Not abundant, but is found frequently in smaller 

 ponds of Pennsylvania and Xew Jersey. 



This form is near C. pulchernmiini, Xord., but diflfers in the 

 gaping sinus, the rounded inferior angles of the semi-cells, 

 the number of crenulations, and larger size. 



C. Pseudopectixoides, Wolle. Plate XXII, figs. 16, 17, 18. 



Differs from the typical plant in its smaller size, less num- 

 ber of crenulations, and absence of the series of granules on 

 the Ijasal inflation ; instead the granules are scattered. 

 Diameter 30-35 j-t. 



Have this form from Florida, from the White Mountains, 

 N. H., and the Lehigh Valley, Pa. 



C. NASUTUM, Xord. Plate XXII, fig. 19. 



Nearly one-fourth longer than broad, constriction forms a 

 narrow linear sinus; semi-cells semicircular, margins incised- 

 crenate, crenae eight, smooth or granulate ; cytioderm rough 

 with eight radiating series of granules; end view oval with 

 an inflation on each side. 

 Diameter 30-36 ju- 



Rare, diflfers from the typical, Arctic form in being smoother, 

 not so strongly marked with coarse granules. 



