L893.] NATURAL SCIENCES OF I'll I I.AllKLPH I A. 4H< 



ON SOME LEECH-LIKE PARASITES OF AMERICAN CRAYFISHES. 



By .1. PERCY MOORE. 



In 1851 Dr. Leidy described in the Proceedings of this Academy 

 the external characters of Astacobdella philadelphica, which he 

 found occupying generally the exterior of Cambarus bartonii. This 

 account was quoted in full in the Synopsis of American Freshwater 

 Leeches published in 1874 by Verrill, who adds no observations of 

 his own. Other than these the writer is acquainted with no 

 published accounts of American Discodrilidse (Vejdovskv). At- 

 tracted by the peculiar structure, the uncertain affinities, and most 

 of all, by the remarkable variability of these parasites, a score 

 of zoologists have been led to contribute to our knowledge of 

 the European forms. The question of the specific distinctness or 

 unity of the several forms which take up their abode on Astaeiis 

 fluviatilus has led to considerable discussion, which has not yet 

 reached a . definite settlement. Vejdovskv believes the three or 

 four forms which have been described as distinct species to be but 

 varieties of one extremely variable species — a view to which a strong 

 support is lent by the elaborate tables of variations prepared by 

 Voigt. Whitman has found living on the crayfishes of Japan a 

 similar multiplicity of forms, which have been regarded as constitut- 

 ing three distinct species, but which have not, the writer believes, 

 been described. 



It now appears that our American crayfishes likewise carry about 

 with them a heterogeneous burden of leech- like parasites (or mess- 

 mates?). Our common Cambarus bartonii, for example, is affected by 

 at least four forms, which are easily distinguished, and which will be 

 here described as specifically distinct. Other and different forms have 

 been found by the writer on ('. affinis and on C. which in- 

 habits the larger mountain streams of western North Carolina. These 

 being the facts, the writer thought it well to present for publication 

 the present short account, which is entirely preliminary to a more 

 complete discussion of the structure and affinities of these Annulata, 

 the first instalment of which will soon appear. It is hoped that this 

 paper will serve to direct the attention of zoologists to this neglected 



