150 Lake Maxinkuckee, Physical and Biological Survey 



28. DI( TYOSPH^ERIUM EHRENBERGIANUM Naegeli 



Not a plankton form ; staying near shore and obtained in hand- 

 gathered material along with Oscillatoria, Rivularia, (Edogonium, 

 etc. It occurs in only one sample. 



29. TETRAEDRON MINIMUM (A. Braun) 



Common among material found in the contents of mussel stom- 

 achs along with Scenedesmus, Pediastrum, etc. On account of its 

 small size it is easily ingested by the mussels. 



30. CHORELLA sp. 



Common, associated with Ophrydium, which is one of the most 

 abundant protozoans in the lake. 



31. EREMOSPH^RA VIRIDIS de Bary 



A common element of the plankton occurring in most of the 

 vertical hauls at the established stations. It is said to be "a con- 

 stant associate of certain desmids" in the British Isles, where it is 

 especially common in Sphagnum bogs. 



32. ANKISTRODESMUS sp. 



Various forms of Ankistrodesmus are common elements of the 

 mussel food. This genus is perhaps better known under the name 

 Rhaphidium. 



33. SCENEDESMUS ABUNDANS Kirchner 



Various forms of Scenedesmus, especially abundans and obliquus, 

 as well as numerous forms for which no descriptions or figures 

 could be found, were abundant elements of mussel food. Indeed, 

 along with Pediastrum, they may be regarded as the most charac- 

 teristic elements of the mussels' bill of fare. They were especially 

 common in Lost Lake. 



34. SCENEDESMUS OBLIQUUS (Turpin) 



Common in towings taken near the shore. 



35. CRUCIGENIA TETRAPEDIA (Kirchner) 



Rare ; only a few colonies seen mixed up in collections of minute 

 algae. Its striking appearance, a flat plate composed of an aggre- 

 gation of minute green maltese crosses arranged in regular order, 

 attracts attention at once. 



3(i. SORASTRUM sp. 



Not a rare plankton element along the edge of Lost Lake, where 

 it is occasionally taken in as food by the mussels. 



