

392 Miscellaneous. 



Belgique, xxiv. 1850), and by Ed. Claparede (Zeitschr. f. wiss. Zoolo- 1 



gie, 1868, p. 445). 



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

 marking of the mite, applies to ours ; and, further, Prof. Leidy 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 interior irregular lozenge spot. Sides brown, 

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

 spots. Limbs grey, translucent, with the chitinous investment 

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

 minal joint of the palps ending in three minute uncinate denticles. 

 Anal plates of the females usually with about 18 to 22 acetabula to 

 each. Length of body 1-375 to 1*75 millim., breadth 1*125 to 1*5 

 milliin. Inhabits the branchiae and mantle of Anodonta Jluviatilis. 



The colours depend mainly on the contents shining through the 

 transparent chitinous investment, which under reflected light ex- 

 hibits a bluish-black tint. Commonly the black colour 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 

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



The number of acetabula to the anal plates is variable ; in one j 



mite the speaker 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 

 European mite aje such as occur among individuals of either ; and 

 Prof. Leidy therefore saw nothing distinguishing ours as a different 

 species. Claparede describes another mite which infests the European 

 Unios, which he distinguishes under the name of Atax Bonzi. The 

 speaker had also observed a different mite, infesting the common mussel 

 (Unio complanatiis) of the Delaware river ; of this mite he exhibited 

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

 Bonzi ; but the question can only be positively answered after the 

 examination of certain details, which he hoped soon to have the 

 opportunity of making. 



If our two parasitic mites are identical with those of European 

 mussels, it not only makes it appear probable that they are of com- 

 mon origin, but renders it the more probable that this is likewise 

 the case with their hosts, even if these are not regarded as of the 

 same species. — Proc. Acad. Nat. Sci. PhilacL Feb. 13, 1883, p. 44. 





