MICKASTERIAS. 39 



This species appears related to M. radiosa, var. ornata, 

 Nord., but is smaller; the lobes are not so deeply, nor so 

 often intersected, and the polar lobe is more exserted and 

 more dilated at the end. 



M. APICULATA, Menegh. Plate LVI, fig. 3. 



Large orbicular or oblong, with the surface more or less 

 densely covered with macros ; semi-cell five-lobed 5 lateral 

 lobes equal in size, not close, bisected 5 lobulets bifid, each 

 section emarginate, mucronate at each angle; polar lobe pro- 

 minent, widely dilated, center notched, margins mucronate. 



Diameter 175-200 JJL. 



Ponds, Pennsylvania, New Jersey and Minnesota ; rather 

 rare. 



M. MAMILLATA, Turner. Plate LXII, fig. 2. 



Semi-cells papilionaceous, five-lobed ; end lobe broad ; its 

 ends and those of the other lobes divided into palmate 

 shapes, with the points broadly rounded ; surface adorned 

 with maniilliform processes radiately arranged ; provided 

 with a process at isthmus, the purpose of which is ap- 

 parently (?) to strengthen the segmental union. Only one 

 specimen (semi-cell) seen. Seemingly related to M. apiculata. 



Diameter 198 p. 



Inasmuch as this semi-cell was found in collections made 

 in a swampy part of Harvey Lake, Pennsylvania, in which 

 M. apiculata occurs freely, the author would emphasize the 

 last remark. 



M. DENTICULATA. V. Des. U. S. p. 109. 

 A zygospore. Plate LXII, fig. 3. 



From a collection made by W. N. Hastings, Rochester, 

 New Hampshire. 



M. AMERICANA. V. Des. U. S. p. 112, var. SPINOSA, Turner. 



Plate LX, fig. 30. 



A form not strictly from the United States, but near it, 

 may be introduced. Mr. Turner describes it thus: A small 

 compressed form. About one-eighth less in length and 

 breadth than the type. Central portion of segments smooth; 

 lobes ornamented with short stout spines ; the end lobe 

 bearing near its extremity a species of annular rugoso- 

 spinous coronet. 



Diameter 112 /* ; length 136 jw. 

 Pictou, Nova Scotia. 



