Occasional Papers of the Miiseuin of Zoology 3 



Whether the loss of a portion of the tail was due to the heavy 

 parasitic infestation, as the collectors thought, is not determin- 

 able. Snakes sometimes lose a portion of the tail in encounters 

 Avith other animals and it is not uncommon to find "bob- 

 tailed"' snakes/ In less heavily parasitized snakes the tails 

 were slightl}- swollen and the scutes more nearly normal in 

 position. In very lightly infested snakes the presence of para- 

 sites could only be determined by internal examination. A 

 common feature of the preserved heavily infested snakes is 

 the granular appearance of the ventral scutes of the tail 

 region. These granules are minute, immature trematodes or 

 cercariae readily visible to the naked eye and so abundant as 

 to cause the scutes to appear swollen, their posterior margins 

 to be elevated and somewhat projecting from the body. After 

 being for several weeks in the preserving fluid many .scales 

 thus swollen by the parasites had become more or less detached 

 and in some instances the tail was badly macerated although 

 the remainder of the body was well preserved, and unpara- 

 sitized snakes in the same museum jar were in good condi- 

 tion. The parasite present in such numbers proved to "be an 

 hitherto undescribed larval distome for which the name 

 Ccrcaria niarcianac La Rue is proposed. 



Cercaria marcianae, new species. 



Cotypes: ]Museimi of Zoology, University of jNIichigan. 

 •sHde No. 150; paratypes on slides Nos. 149, 151, 152, 153, 154. 

 also alcoholic material in the collection of the Museum, and 

 slides and alcoholic material in the collection of the writer. 



Description : The parasite is a typical tailless distome cer- 



^ One snake with a "bob-tail" but with no external appearance of parasites was 

 caught in Fort Davis. Examination of interna! organs showed that a few parasites 

 Avere present but not in sufficient numbers to account for the loss of the tail. 



