No. 6.] NEW SPECIES OF THE GENUS A TAX BRUZ. 285 



the acetabula, instead of being toward the margin, are over 

 the greater part of the plate, and are larger than in that species, 

 while in the middle of the outer margin, on either side, are two 

 much larger than any of the rest. The number of acetabula 

 in the male varies from 25 to 30, in the female from 30 to 35. 

 Two hundred and ninety-five specimens were obtained at 

 Charlevoix and Grand Rapids, Mich., in various species of Unio. 



VII. A. tmnidiis n. sp. 



Very similar to A. ingens 1 in form and size, the females 

 of both showing a tendency to enormous distension when filled 

 with eggs, in the relative length of the legs, in the habit of depos- 

 iting these in loose masses in the mantle and gill cavities, and 

 also in color, the internal structure of each suggesting no trace 

 of the Y-shaped mark, but the color being a light brown with 

 numerous fine white vermiculate lines. The 

 palpi are very similar in the thickness of the 

 fourth segment and in the presence of four 

 inconspicuous papillae at the tip. The legs 

 are feeble in proportion to the size of the FIG - 6. A. tumid - 



. , .... distal end of distal seg- 



body, as are those of A. ingens, but, unlike ment , fourth pair of 

 that species, the claws are not simple, but are legs ' 

 of the type of A. ypsilopJiorus, though relatively much smaller 

 and heavier (Fig. 6). The sexual area, also shows a marked 

 difference from that of A. ingens and agrees in position, form, 

 number of acetabula, etc., almost precisely with that described 

 for A. arcnata. 



Taken at Lake St. Clair, Ann Arbor, Charlevoix, Interme- 

 diate Lake, and Grand Rapids, Mich., in Margaritana deltoides 

 Lea, Anodonta fragilis Lam., A. edentula Say, and A. ovata 

 Lea, thus an Anodonta parasite, while A. ingens is a Unio 

 dweller. Few specimens were taken in any one locality. 



1 Koenike, I.e., p. 219, Taf. in, f. 65-67. 



