I7<> RESEARCHES IN HELMINTHOLOOY AND PARASITOLOGY. 



Belgiqiie, xxiv, 1850), and by Ed. Claparede ( Zeits. f.wiss. Zoologie, 

 1868, 445). 



Dr. Bonz's description, referring chiefly to the form, color, and 

 marking of the mite, applies to ours, and, further, he thought the 

 description of the details of Claparede applies sufficiently well to 

 the same. 



The characters of our mite are, briefly, as follows : 



Body ovoid, black, with a sulphur-yellow median line, often more 

 or less interrupted, forked in front and ending in an angular spot 

 behind. The yellow marking divides the black into a pair of lateral 

 reniform spots and an anterior irregular lozenge spot. Sides brown, 

 from the eggs shining through. Head gray, with dumb-bell eye 

 spots. Limbs gray, translucent, with the chitinous investment 

 bluish-black, hirsute, ending in pairs of double falcate ungues. 

 Terminal joint of the palps ending in three minute uncinate den- 

 ticles. Anal plates of the females usually with about 18 to 20 

 acetabula to each. Length of body 1.375 to 1.75 mm. ; breadth 

 1. 125 to 1.5 mm. Inhabits the branchia; and mantle oi Anoc/on/a 

 JiiiviatUis. 



The colors depend mainly on the contents shining through the 

 transparent chitinous investment, which, under reflected light, ex- 

 hibits a bluish-black tint. Commonly the black color is intense, 

 and in alcoholic specimens the whole body is black. In several 

 individuals the black passed into a chocolate hue. Dr. Bonz de- 

 scribes the European mite as black, with the median dorsal mark 

 pale yellow; Pfeiffer as red-brown, with a citron-yellow mark, and 

 Beneden says it .shows a Y in white, from which it was named. 



The number of acetabula to the anal plates is variable. In one 

 mite he found 23 to each plate, in a .second 22 to each, in a third 

 22 to one and 17 to the other, and in a fourth 18 to one and 17 to 

 the other. Claparede gives from 15 to 20 as the number to each 

 plate in the European mite. 



The variations of our mite from the characters given of the Eu- 

 ropean mite are such as occur among individuals of either. He 

 therefore saw nothing distinguishing ours as a different species. 

 Claparede describes another mite which infests the European Unios, 

 which he distingui.shes under the name of Ata.x bonzi. The speaker 

 had also ob.served a different mite, infesting the common mussel, 

 Unio co/i/p/iuiatus, of the Delaware river. Of this mite he exhibited 

 a drawing made in November, 1854. He .suspected it to be the 

 Afax bonzi, but the question can only be more positi\ely answered 



