LYMN.EIDJE OF NORTH AMERICA. 393 



appears to be a recognizable race of catascopium, characterized by an 

 elongated, narrow shell, flat-sided whorls and a narrow aperture. 



Galba catascopium adamsi, Var. Nov. Plate XLII, figures 5-8. 



Lymneea catascopium Walker, An. Rep. Geol. Surv. Mich., 1908, p. 291, 

 1909.— Gleasox, 1. c, p. 64, 1909. 



Shell : Thin, narrow, much elongated ; periostracum yellowish 

 or whitish horn; sculpture coarser than in typical catascopium; whorls 

 6-6^2 very flatly rounded, very slowly increasing in diameter but rapid- 

 ly increasing in length ; spire very long, usually longer than the aper- 

 ture, narrow, acute, the whorls very flatly rounded; sutures shal- 

 low ; outer lip but slightly thickened within ; aperture narrow, very 

 elongate-ovate, narrowed above and below and frequently sharply 

 angled ; inner lip rather wide, flatly reflected and tightly appressed to 

 the columellar region, usually completely closing the umbilical chink ; 

 there is a distinct, oblique columellar plait and the parietal wall is 

 covered with a heavy, wide callus ; axis twisted. 



Length. Breadth. Aperture length. Breadth. 



16.00 8.00 9.00 4.00 mill. 



15.00 7.00 7.50 3.00 " 



15.60 7.00 8.00 3.50 " 



Types : Chicago Academy of Sciences, four specimens, Xo. 

 24511 ; cotypes, coll, Bryant Walker. 



Type Locality : St. Clair flats, Detroit, Michigan. 



Animal: Not differing from typical catascopium. 



Jaw: As in catascopium. 



Radula: Xot differing from typical catascopium. There is little 

 variation, there being nine laterals in all the specimens examined. 



Genitalia: (Plate XV. fig. F, 1-3). Xot differing essentially 

 from these organs in typical catascopium. In one specimen from the 

 St. Clair flats, the penis-sac retractor was double (3). The measure- 

 ments of the genitalia will be found under typical catascopium (p. 385) 

 where they are listed for comparison with the typical form. 



Range : Adamsi has not been seen outside of the state of Michi- 

 gan and is, hence, confined to the Canadian Region. 



RECORDS. 



Michigan : St. Clair flats, "Wayne Co. ; small island in Tobin Harbor, 

 Isle Royale (Walker). 



Ecology : "Apparently most frequent in shallow water in places 

 sheltered from the waves." (Isle Royale) St. Clair flats (Detroit). 



Remarks: The race here separated from catascopium offers 

 characters which easily separate it from the typical form, which is 

 always wider, with a shorter, wider spire and a more ovate aperture. 



