412 Ill'nwis St<(te lAihordtory of Natural History. 



abundant parasites, and also the maximum, minimum, and 

 average number of these parasites found in the hosts. The 

 frequency of occurrence of any one of these parasites in 

 relation to the total infestation of a species is to be learned 

 by a comparison of Tables III. and IV. Thus in a total of 

 fifteen hundred and seventy-seven examinations, — in which 

 seventy- four per cent, were in some measure infested (Table 



Table IV. Comparison of Infestation by Different Parasites. 



HOST SPECIES. 



Names. 



Percentage of 



hosts infested 



with 



Number of 



parasites in 



one host. 



Average No. of 



parasites in 



one host. 



Quadrula multiplicata. . 

 tuberculata. . . 



metanevra 



lachrymosa. . . 

 asperrima .... 



pustulata 



pustulosa 



28 11 



plicata 

 tri^ona . . . 

 rubioinosa 



ebeiia 



Unio oibbosus 



coniplanatus 



Ala.smodonta confragosa. 

 complanata 



rugosa 



marginata. 

 Strophitus edentulus. . . . 



Anodouta imbecilis 



suborbiculata . 

 corpuleuta.. . . 



Obli(iuaria reflexa 



Plagiola eleo'ans ' 



donaciformis.. . . 



Lamjisilis parvus 



ellipsis 



ligamentiuus. . 



luteolus 



anodontoides . 



rectus 



ventricosus . . . 



alatus 



gracilis 



41 

 36 

 29 

 21 

 20 

 87 

 89 

 27 

 40 

 23 

 35 



137 

 3 



64 

 18 

 51 

 36 

 49 

 20 

 45 

 32 

 48 

 37 

 31 

 14 

 91 

 25 

 62 

 49 



108 

 60 

 89 



80 

 33 

 72 

 100 

 25 

 32 

 70 

 11 

 25 

 30 

 26 

 27 

 26 

 16 



18 

 17 

 51 

 100 

 82 

 9 

 63 

 57 

 65 

 86 



i2 



76 

 14 



28 

 82 

 87 



3 



1 



3 

 33 

 50 

 76 



8 

 20 

 75 



71 1 

 41 1 

 S3 1 



3 1 

 . ... 1 



7 !r 



22 



48 

 61 

 65 



67 

 80 1 



64 11 



191-8 

 6 

 41 

 13. 



5 1-7 

 5 1-2 

 •20 ... . 



•6 1-2 

 ■6 ... 

 ■24 .. 



-7 .... 

 ■281 . . . 

 -751-4 

 -85 1 



1- 



1- 



l-i 



1- 



1-2 

 1-7 

 1-86 

 1-92 



1 

 1-5 

 1-8 

 1-5 

 1-6 

 1-9 

 1-15 

 1-10 

 1-12 



1 

 1 



Eggs 

 1 

 2 

 3 

 8 



Eggs 

 3 

 8 

 2 

 2 

 1 



4 

 2 

 3 

 4 

 3 

 3 

 50 



Totals 1577 41 



18 



37 



