224: THE CHICAGO ACADEMY OF SCIENCES. 



GENITALIA : In almost all respects like those of cubensis and 

 techella. Measurements are as follows : 



Prost. Penis-sac 



Penis. Penis-sac. Vas. def. duct. Rec. sem. Penis ret. ret. Shell. 



1.25 2.00 8.00 2.00 2.00 1.10 1.50 7.00 



The penis-sac retractor is much enlarged as it enters the penis-sac, 

 the whole muscle forming a broad band of tissue ; the penis retractor 

 is long and narrow, and enters the columellar muscle at the same point 

 as the penis-sac retractor. The receptaculum seminis is ovate-quad- 

 rangular in outline. 



RANGE : Colorado. A species of the Coloradoan region. 



RECORDS. 



COLORADO: West of Fort Collins, Larimer Co. (Henderson). 



ECOLOGY : Inhabits lagoons and intermittent bodies of water. Mr. 

 Henderson writes of the habitat as follows : "I am informed that there 

 had been no water in the lagoon for many months, probably not sinoe 

 last summer or autumn. The ground was cracked to a depth of 

 several inches and the mollusks were found down in the cracks and 

 in the mud. Therefore, it seems to be another species capable of 

 aestivating." 



REMARKS: This species was at first thought to be Galba sono- 

 mcensis Hemphill, but a comparison with that species shows that the 

 present species differs not only from sonomcensis but from all related 

 species in the form of the spire and aperture. The first two whorls 

 cf the spire are coiled in the same plane, producing a sharply truncated 

 appearance. The outline of the shell is also more ovate than in sono- 

 mansis and the aperture is not expanded. The inner lip is also rolled 

 over to a greater extent than in the Sonoma species, and approaches 

 closely to some individuals of bulimoides. The only Lymnaeid likely 

 to be confounded with hendersoni is sonomcensis, which differs in the 

 form of the spire and inner lip. 



I take great pleasure in dedicating this interesting species to Judge 

 Junius Henderson, of the University of Colorado. 



Galba perpolita (Dall). Plate XXVIII, figure 19. 



Lymnaa (Stagnicola) perpolita BALL, Alaska Moll., p. 78, pi. 2, figs. 6, 8, 

 1905. 



Lymn&a perpolita PILSBRY, Nautilus, XIX, p. 95, 1905. 



"SHELL : Small, translucent, dark amber color, with a darker line 

 at resting stages; smooth, except for fine lines of growth, brilliantly 

 polished; whorls four, tumid, rapidly increasing, separated by a pro- 

 nounced suture ; spire short, rather obtuse ; aperture ovate, longer than 

 the spire, with a very thin wash of callus on the spire, the pillar lip 



