MUSSEL FAUNA OF MAUMEE EIVER. 



69 



produces no stain at all. The discolorations frequently found m the 

 umbones of mussel shells can not all be attributed to it, since in one 

 pond where such stains are very frequent, no distomids could be 

 found. In general, it is a baroque former rather than a stain pro- 

 ducer. In some localities it especially attacks Unio gihhosus and 

 Quadrula tuberciilata^ and the host mussels are peculiarly prolific 

 in baroques. Most of the dorsal baroques which the clammers save 

 and sell to dealers in jewelry are probably formed through the ac- 

 tivities of this parasite. The baroques are known among the clam- 

 mers as " chicken feed " and usually bring about $2 per ounce on the 

 ground. In many places this material is fairly common and is a 

 source of revenue among the clammers. 



It is probable that the distomids which stray into large heavy- 

 shelled mollusks fall out of the normal course of their life history 

 unless they again migrate to thinner-shelled species, for the thick- 

 shelled mussels, after they have grown, are proof against fishes, musk- 

 rats, or any other predaceous animals, and live to die a natural 

 death, or in these recent times to fall a prey to the clammer. This 

 gives the parasitic distomid no opportunity to enter into another 

 host in the usual manner. Crawfishes eat mussels that have died; 

 but so far as known the host of the mature distomid is always a 

 vertebrate. 



Moreover, on the supposition that the distomids found in the 

 heavy-shelled mollusks are migrants from Anodonta^ Strophifus, or 

 other thin-shelled species, these mussels, which are regarded as 

 valueless by the clammer and destroyed by the wholesale, are of im- 

 portance as an intermediary in the formation of baroques and perhaps 

 all distomid- formed pearls. Similarly, though in a somewhat dif- 

 ferent manner, the cockle, Cardiinn^ acting as an intermediate host 

 between a species of mussel-eating duck and the salt-water mussel 

 Mytilus^ brings about pearl formation in the latter species, as shown 

 in the investigations by Jameson « of pearl formation in Mytilus. 



6. BucefJialus jyolymorphus (von Baer). — During the Maumee in- 

 vestigations this species was encountered in only one instance, when 

 an example of Lampsilis luteohis^ obtained near the mouth of the St. 

 Joseph Kiver, was found to be affected. In investigations outside 

 the Maumee Basin it was not infrequently met. According to Kelly, 

 who has had considerable experience with mussel parasites, it is 

 fairly common, though not so common as Aspidog aster ^ Atax^ or 

 Conchopthinis^ and affects a large number of species of mussels. 



Bucephalus polijmorplius is of considerable economic significance, 

 since it has been shown by von Baer and later by Kelly that this 

 species (and, as Kelly has pointed out, some other distomids as well) 

 frequently affects the generative tissue of the host mussel to such an 



" Proceedings Zoological Society London. a^gI. \, 1902, pt. 2, p. 140-166. 



