DICTYDIMTIIALWM 215 



and ovoid or flattened on one side; when free, globose, very minutely 

 spinulose, 9.5-10.5. 



Colorado: Dr. Sturgis. 



3. Dictydiaethallum Rostafinski 



1873. Dictydiaethalium Rost., Versucli, p. 5. 

 1875. Clai/iroptyc/iium Rost., Mon., p. 224. 



iEthalium depressed, flat; the sporangia erect, regular, prismatic 

 by mutual pressure, the peridia convex above, v^^anting at the sides 

 and within the aethalium represented by vertical threads marking 

 the angles and passing from base to summit. ■ 



This genus is readily recognized by the internal structure of the 

 sethalium. The lateral wall-openings, which, as we have seen, char- 

 acterize the sporangia of the preceding genus, here become ex- 

 treme, occupying to such extent the lateral wall-space of each spor- 

 angium that only threads remain to mark the vertical angles. 



In 1873 Rostafinski applied the generic name here adopted, be- 

 cause he thought he discovered close relationships with Dictydium. 

 In 1875, believing his first impressions erroneous, and desirous that 

 the nomenclature might not at once mislead the student and per- 

 petuate the memory of his own mistake, the same author proposed the 

 name by which the genus has generally ever since been known — 

 Clathroptychium. However sensible the latter conclusion reached 

 by our Polish author, it is plainly contrary to all rules of priority. 



Our region shows but a single widely distributed species, — 



1. DlCTYDI^.THALIUM PLUMBEUM {Schum.) Rost. 



Plate I., Figs. 2, 2 a, 2 b. 



1803. Fuligo plumbea Schum., Enum. Saell., No. 1410. 



1833. Licea rugulosa Wall., Cr. Fl. Ger., IV., p. 345 



1873. Dictydtaetlialium plumbeum (Schum.) Rost., Versuch, p. 5. 



1875. Clathroptychium rugulosum (Wallr.) Rost., Mon., p. 225. 



1894. Dictydiaethalium plumbeum Rest., List., Mycetozoa, p. 157. 



^thalium thin, very flat, olivaceous or ochraceous, smooth, under 

 the lens punctate, in section showing the columnar or prismatic spo- 

 rangia, which are normally six-sided, having at the edges six simple 



