72 Natural History Bulletin. 



CLASS.— LANlBIvIvIBRANCHI ATA. 



ORDER.— SIPHONIDA. 



FAMILY— CYRENID.^. 



Genus S-phceriiim. — Sco-poli. 



S. SULCATUM. — Lam. 



Common in small streams and ponds. 

 S. STRiATiNUM. — Lam. 



Very common on mud and sand in creeks and rivers. 



S. SOLIDULUM. — Pr. 



Formerly very common in the Iowa river, but now largely 

 displaced by the preceding species. 



S. STAMINERUM. Con. 



The only specimens known to us were found by us near 

 Iowa City. Only three or four specimens were observed. 

 A pretty species for which some forms of S. sulcatum are 

 often mistaken. 



S. RHOMBOIDEUM. Say. 



Not common. It occurs in ponds. One of the prettiest of 

 Sphasriums. 

 S. FABALis. — Prime. 



Rare. Only three specimens were found by us near Iowa 

 City. 



S. PARTUMEIUM. — Say. 



Quite common in ponds near Iowa Cit}"^ where it occurs 

 with the following species. The species does not seem to be 

 as gregarious as most of the Spheeriums. 

 S. JAYANUM. — Prime. 



Less common than the preceding. Specimens collected 

 near Des Moines by Mr. C. R. Keyes are in the University 

 Cabinet. 



S. TRANSVERSUM. Say. 



One of the most common species of the genus. Found in 

 mud in ponds and sluggish streams. 



