78 Calcareous Pebbles formed by Alga. 



DIATOMACEOUS REMAINS OBSERVED IN PREPARA- 

 TIONS OF CALCAREOUS ALG^E FROM A POND 



IN MICHIGAN. 



Achnanthes delicatula, Grun. Scarce. 

 microcephala, Grun. 



minutissima, K. 



var. cryptocephala, Grun. 



Achnanthidium flexellum, Breb. 

 Amphipleura pellucida, K. Rare. 

 Amphora ovalis var. affinis, K. Rare. 



veneta, K. Frequent. 



Asterionella formosa, Hass. Rare. 

 Caloneis alpestris, Cl. 



fasciata, Cl. Rare. 



obtusa, Cl. Rare. ( = Nav. Hebes, Ralfs.) 

 Cocconeis Placentula, E. 



var. lineata, Grun. Rare. 



Cyclotella antiqua, W. S. 



comta var. radiosa, Grun. 

 Kiitzingiana, Chauvin. 

 Meneghiniana, K. 

 Cymatopleura elliptica W. S. (A twisted form, perhaps the C. 



Cochlea, Brun. 

 Solea, W. S. 



Cymbella amphicephala, Naeg. 

 angustata, W. S. 



aspera, E. (C. gastroides, K.) Rare. 

 var. minor, K. Rare. 



Cistula, Hempr. 

 ,, delicatula, K. 

 Ehrenbergii, K. Rare. 

 hybrida, Grun. Rare. 

 leptoceros, K. 

 microcephala, Grun. 

 parva, W. S. 



