Lake Maxinkuckee, Physical and Biological Survey 151 



37. CCELASTRUM MICROPORUM Naegeli 



Common in plankton hauls along shore, and a frequent element 

 in the material forming the food of mussels. 



38. CO2LASTRUM SPH^ERICUM Naegeli 



Probably common along shore and quite frequently found in the 

 algal mixtures taken from mussel stomachs. 



39. PEDIASTRUM BORYANUM (Turpin) 



Occasional but not abundant, occurring in a number of the ver- 

 tical plankton hauls and now and then in towings along shore. 

 Usually only one or two taken in a gathering. The mussels are the 

 best collectors of Pediastrum, almost every stomach examined con- 

 taining from one to several examples. 



40. PEDIASTRUM DUPLEX Meyen 



Occasionally taken in towings near shore. Variable in length 

 of horns, etc. Characterized by the perforate disk. Like the other 

 Pediastrums it appears to be a favorite food for mussels; indeed, 

 the best way to obtain examples of Pediastrum is to examine the 

 intestinal contents of mussels which almost always have present 

 representatives of some of the species. 



41. PEDIASTRUM EHRENBERGII (Corda) 



Not common ; a good example obtained among algaB in the Out- 

 let near the bridge on July 23, 1906, among the marl-like blue ma- 

 terial. In general form the example found agrees with Wolle's 

 figure (Desm. U. S. PI. LIII, fig. 25) of the 4-celled phase of this 

 species, but differs markedly in the inner cusps of the cells, which 

 are bluntish. Diameter of the ccenobium 18 mic. It is probably the 

 young of the variety represented by Wolle's fig. 27. A peculiar 

 form of what appears to be this species is rather common in the 

 lake, and reaches a large size. Its most striking peculiarity con- 

 sists in having the interior cells of the colony retain their horns in 

 a rudimentary form so that each cell has a markedly concave side. 

 This form is most frequently found along shore where the bottom 

 is shallow and the bottom more or less a black mud, as at Norris 

 Inlet and the Outlet. 



42. HYDRODICTYON RETICULATUM (Linnaeus) 



Not taken in plankton but represented in a hand-gathering along 

 with Spirogyra, CEdogonium, etc. Not especially common about the 

 lake; indeed, not so common as one might naturally expect, but 



