34 THE CHICAGO ACADEMY OF SCIENCES. 
other areas. The total number of species and varieties is 153, 
distributed among twenty families and fifty genera. These 
may be primarily grouped as follows: 
tT LANALIVE SPECIES AAC VARICES, c1.u+-.0 > vs <.;s +s 0 a.2 piv a0 ae a ae pad 
2. Introduced species........... JAG Bo MORESO Hoe TES. 6. Wate tans sie i ee a 6 
Total number of species.............. eet oe 153 
1. SYSTEMATIC DISTRIBUTION. 
GROUP. Orders. Families. Genera. Sp. & Var. 
Gastropoda «neato oe 3 18 38 108 
Pelecypoda..... Sid byes Shs 2 2 12 50 
Motals eee eieaos 5 20 50 153 
GROUP. Chicago. Wises 
UGTA! ree ie ee crs ty cada ER oe STR Ee 20 35 
GeONErAY sls mers aici ceo ene been eltele rere eee 50 98 
SPECIES cl. Byetaraterstes telsus coe clovmben hah see Ree ice ee 147 3000 
PIVATIOHES Oo Ate cele cities 2 sete eel: hee ee 6 300 
3. COMPARISON WITH MICHIGAN. 
GROUP. Chicago. Michigan. + 
MAMIIES Si Goes he eh. c bcs Ohls D ee eee - 20 17 
SEDO A e.g Kiely, | Sieve lets ere ie leket ero ue eae ecto aal «gau 50) 49 
SPECIES ios 225 o.o'n, sts ho 0s ect embnleete cnet oereptemeraloats 147 246 
MAEICEIOS oi oh lcidie e chele te | Ree ae or ny aes ee ee 6 19 
4. COMPARISON WITH PENNSYLVANIA. 
| Philadelphia 
GROUP. Chicago. | Quceneny |, and 
ONS Envivonis 
Pamilies so ws ngs seb Rea eens 20 15 19 
i) AINE ere Merge sys 2 Sis) 50 30 40 
Species: sie: ite eee 147 91 84 
WArlGeS 5. Lia scp on yee eee 6 2 3 
*The numbers for the United States are only approximate, as there is no recognized 
catalogue of the mollusks of this region. 
+ ‘‘The Shell-bearing Mollusca of Michigan,’’ by Bryant Walker, The Nautilus, Vol. VI., 
PP. 13, 31, 42, 63, 135. In all these tables, some species and varieties considered distinct by 
the authors are here considered synonyms, the better to compare with the present list. 
¢ ‘Land and Fresh-Water Shells of Allegheny County, Pa.,’’ by S. H. Stupakoff. The 
Nautilus, Vol. VII., p. 135; Vol. VIIL., p. 116. 
\| ‘*Mollusk Fauna of Philadelphia and Environs,” by Morris Shuck. The Nautilus, 
Vol. VIII., p. 133. 
