140 THE NAUTILUS. 



below the suture, and to the 6th whorl the caliber of the shell de- 

 creases slightly. Beyond this the caliber increases slowly, and the 

 riblets gradually become longer, though a smooth band persists along 

 the middle of each whorl as far as about the 16th whorl, after which 

 the ribs are continuous. 



The above forms, with others, will be figured in a future report on 

 the shells collected by Mr. Hinkley. 



A NEW SPECIES OF LYMNJEA. 



BY FRANK C. BAKER. 



LYMN^EA HENDERSONI n. sp. 



Shell globose, very thin and fragile; periostracum light yellowish 

 or brownish-horn; surface dull; sculpture of fine growth-lines, without 

 spiral lines; whorls 3^, very rapidly increasing in diameter, the body 

 whorl seven-eighths the length of the entire shell, very globose; spire 

 very short, depressed, dome-like, the first two whorls flat and coiled 

 in the same plane so that a profile view shows only two full whorls. 

 Nuclear whorls flat, partly concealed by the volutions of the spire; 

 sutures impressed; aperture round or roundly elliptical; outer lip thin; 

 inner lip broad, triangular, reflected over the columellar region, but 

 leaving a deep, well-marked chink; the inner edge of the inner lip is 

 usually bent downward near the body whorl, partly concealing the 

 umbilical chink; parietal callus thin; axis smooth, hourglass-shaped. 



Length 7.00, breadth 5.50; aperture length 4.75, breadth 3.00 mm. 



Length 6.25, breadth 5.00; aperture length 4.00, breadth 2.50 mm. 



Length 6.75, breadth 5.00; aperture length 4.80, breadth 3.00 mm. 



Length 5.50, breadth 4.10; aperture length 4.00, breadth 2.50 mm. 



Types: Chicago Academy of Sciences, six specimens, No. 24534; 

 Co-types : University of Colorado, Boulder, Colo. 



West of Fort Collins, Laramie county, Colo. 



Ecology: Inhabits lagoons and intermittent bodies of waters. 

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

 that there had been no water in the lagoon for many months, prob- 

 ably since last summer or autumn. The ground was cracked to a 

 depth of several inches and the mollusks were found down in the 

 cracks in the mud. Therefore, it seems to be another species cap- 

 able of aestivating." 



