COSMABIUM. 89 



Diameter 45 f..; length 6<> //.; somewhat variable in size. 



A resemblance to forms of many sea side shells suggested 

 the name. Not abundant but is found frequently in smaller 

 ponds of Pennsylvania and New Jersey. 



This form is near < '. pulcherrimum, Nord., but differs in the 

 gaping sinus, the rounded inferior angles of the semicells. 

 the number of crenulations, and larger size. 



( '. Pseudoi'K* tinoii>i>, Wolle. Plate XIX, figs. 16, 17. 18. 



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

 ber of crenulations, and absence of the series of granule- oh the 

 basal inflation, instead the grannies are scattered. 



Diameter :;()-:',.") u.. 



Have this form from Florida, from the White Mountains, 

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



('. NASUTUM, Nord. Plate XIX, fig. 1!'. 



Nearly one-fourth longer than broad, constriction forms a 

 narrow linear sinus; semicells semicircular, margin- incised- 

 crenate, crense eight, smooth or granulate; cytioderm rough 

 with eighl radiating series of granules; end view oval with an 

 inflation on each side. 



Diameter 30-36 fl. 



Rare, differs from the typical, arctic form in being smoother, 

 not so strongly marked with coarse granules. 



C. PYCNOCHONDRUM, Nord. Plate XIX. figs. 10, 11. 



About one-fifth longer than the diameter; subhexagonal, 



constriction deep, sinus narrow linear; end truncate quadri- 

 crenate ; angles inferior and superior obtusely rounded ; side- 

 moderately convex with about six crense each ; at base nine 

 to twelve vertical, or somewhat diverging -eric- of granule- ; 

 membrane ornate with additional granules arranged in lines, at 

 the same time radiating and concentric ; the former courses are 

 double, and often triple near the margin ; central area within 

 the concentric rows, is nude. Seen from the vertex, or from 

 the side, a basal inflation is evident ; thickness of the cells, 

 equal to about half the length ; isthmus measures about half 

 as much as the breadth. 



Diameter 50 fi. ; length 79 //. 



