THE MOLLUSCA OF COLORADO 95 



northeast of Greeley, and have as yet been found nowhere else in Colorado. Dr. Sterki 

 writes: "A species from the Mississippi Valley, etc., may possibly be of the same species> 

 not described so far as I know." 



Specimens collected by Prof. Beardsley in the Cache la Poudre, near Greeley, much 

 resemble 5. striatinum Lam., but the shells are heavier and there are other minor differ- 

 ences. Another lot obtained by the same collector at the head of Rio Grande Canyon, 12 

 miles from Antonita, Conejos County, do not seem referable to any known species. 

 Further material, especially from other localities, and further study of these two forms 

 are desirable before deciding whether they are new. A few dead shells collected by Prof. 

 E. Bethel near Meeker are near S. striatinum. 



Genus CALYCULINA Clessin 



Calyculina partumeia Say. 



SphcBrium partumeia, Saguache and Rio Grande, Yarrow 68, 949, 950. 

 Calyculina securis Prime. Fig. i (enlarged +|). 



A few rather small specimens, not quite typical in surface appearance, 

 were collected by Mr. D. M. Andrews in a small lake between Magnolia and 

 RoUinsville, in the mountains west of Boulder. Further specimens from 

 Fig. I other localities are desirable, to determine whether the variation is constant. 



Calyculina rykholti Norm. 



Saguache, Sterki 60, 93. Specimens referred to this European species with hesitation. 



Genus PISIDIUM Pfeiffer 



Pisidium abditum Hald. Fig. 2 (very much enlarged). 



Hot Springs, Animas Valley and St. Mary's Lake, Inger- 

 soll 35, 407. Empire, IngersoU 37, 134, Middle Lake of 

 the Clouds, Powderhorn and East Fork Surface Creek, 

 _^_ Cockerell MSS. 



Fig. 2 

 Pisidium noveboracense Prime. 



We have obtained a few specimens from a ditch east of Boulder, but they are "small 

 and not characteristic " (Sterki MSS.). 

 Pisidium variabile Prime. 



Rio Grande of Colorado, Yarrow 68, 951. Custer Co., Cockerell 22, 64. 

 Pisidium compressum Prime. 



Found by the University Pawnee Butte expedition in a small stream emptying into 

 the Big Thompson near Loveland. 

 Pisidium friersoni Sterki. 

 Denver, Sterki 61, 20. 



Prof. Cockerell, to whom Dr. Sterki's specimens were credited, informs me that they 

 were in fact collected by Prof. E. Bethel. We have collected the species from Owen's 

 Lake and ditches east of Boulder and have received a few collected by Prof. E. A. Kenyon 

 at Florence. 



The Pisidia of Colorado are not sufficiently understood at present. The writer has 

 collected several forms in the mountains west of Boulder, up to an altitude of over 10,000 



