12 



ILLINOIS STATE GEOLOGICAL SURVEY 



whorls including the nucleus; sculpture of 

 many close-set, distinct ribs, which become 

 finer on the base, there being usually an al- 

 most smooth space in the center of [the] 

 lower part of the body whorl; aperture 

 widely or roundly lunate, arched above where 

 the outer lip joins the body whorl; peris- 

 tome simple, acute, without parietal callus, 

 the terminations of the outer and columellar 

 lip being widely separated." 



Height, 3.6; diameter, 6.5 mm. (Baker's 

 measurements.) 



Type locality: Three and one-half miles 

 east and one and three-quarters miles south 

 of Lewistown, Fulton County, Illinois. 



Collector: H. R. Wanless, summer, 1927. 



Age designation: Pleistocene, Peorian 

 loess. 



Remarks: Three paratypes in the ISGS 

 collection bear the same number as the holo- 

 type; other paratypes, ANSP, no. 145108. 

 Many lots in the ISGS collection from Wis- 

 consin loess are identified as G. macclintocki, 



GONYODISCUS MACCLINTOCKI ANGULATA 



Baker, 1927 

 Discus macclintocki angulata (Baker) 



Plate 2, figures 13-15 



Holotype: Cat. no. P2359, ISGS. 



Original description: Nautilus, v. 41, p. 

 134, April 1927. 



"Shell differing from typical macclintocki 

 in having a more depressed somewhat flat- 

 tened spire, flatter base and shallow umbili- 

 cus, and a subangulated periphery. On the 

 average rather larger than the typical form." 



Height, 2.9; diameter, 6.2 mm. (Baker's 

 measurements.) 



Type locality: Four miles west of bridge 

 at Havana, in Fulton County, Illinois. 



Collector: H. R. Wanless, summer, 1927. 



Age designation: Pleistocene, Yarmouth 

 loess. 



Remarks: Two damaged paratypical speci- 

 mens, bearing same number as the type, are 

 in ISGS collections; other paratypes, ANSP, 

 no. 144922. 



Baker remarks (p. 134) : "This angulated 

 form persisted throughout the Yarmouth in- 

 terval and died out in the Peorian, a few 

 scattered specimens having been seen among 



a large number of the rounded-whorled Pe- 

 orian form." 



Gyraulus cressmani Baker, 1942 

 Plate 3, figures 1-3 



Holotype: Cat. no. P7453, ISGS. 



Original description: Nautilus, v. 55, p. 

 130, April 1942. 



"Shell of about the size of Gyraulus ver- 

 micularis (Gould), of 3%-4 rounded whorls 

 rapidly increasing in diameter, the sutures 

 deeply impressed, the inner whorls of the 

 right side below the level of the body whorl ; 

 left side with rounded whorls and deep su- 

 tures; periphery rounded and obliquely de- 

 flected; sculpture of coarse growth lines, 

 sometimes slightly costate, with more or less 

 deeply incised spiral lines." 



Height, 1.5; greater diameter, 4.0; lesser 

 diameter, 3.3; aperture height, 1.0; diameter, 

 1.5 mm. Holotype. (Baker's measurements.) 



Type locality: South end of Lower Klam- 

 ath Lake, sees. 25, 26, T. 47 N., R. 2 E., Mt. 

 Diabolo Merid., Siskiyou County, California. 



Collector: L. S. Cressman. 



Age designation: Late Pleistocene. 



Remarks: The ISGS collection has seven 

 paratypic examples, no. P7454. 



Gyraulus pattersoni Baker, 1938 

 Plate 2, figures 4-6 



Holotype: Cat. no. 26128, Chicago Nat- 

 ural History Museum (formerly Field Mu- 

 seum of Natural History). 



Original description: Nautilus, v. 51, p. 

 129, April 1938. 



"Shell completely discoidal, flat on upper 

 and lower sides (right and left) ; periphery 

 flattened and almost as high as the height 

 of the shell, a rounded angle bordering the 

 body whorl above and below; whorls 3^2> 

 slowly and regularly increasing in diameter; 

 sutures well impressed ; sculpture consist- 

 ing of fine lines of growth crossed by fine 

 spiral lines; on the nucleus only the spiral 

 lines are developed, the growth lines begin- 

 ning at about a fourth of the turn of the 

 first whorl; aperture not expanded, wider 

 than high, roundly flattened at the upper part 

 (the shell is ultradextral), almost horizon- 



