2 PROCEEDINGS OF THE NATIONAL MUSEUM V0L> 124 



indicate that this does not occur and that the distributional patterns 

 of the branchiobdellids do not conform to those of their astacid hosts. 



The origin of the taxonomic problems I am involved with go back 

 to the early days when the casual students of the branchiobdellids 

 held such broad generic concepts that there was a tendency to assign 

 any species not quite obviously distinguished by peculiarities of body 

 form and ornamentation to the European genus Branchiobdella. 

 Pierantoni (1912, p. 8), in the first monograph of the order, listed five 

 genera, mostly separated by such characters of body form, though he 

 was aware of the distinctive difference (one testicular segment as 

 opposed to two) between the genus Branchiobdella and the other 

 genera. In addition, he and perhaps others worked with material 

 recovered from the bottoms of museum jars in which crayfish collec- 

 tions were stored. Such material almost invariably is in such a poor 

 state of preservation that specific diagnoses or even generic assign- 

 ments are difficult, doubtful, and often futile. 



Moore (1894) in his work on branchiobdellids during the time when 

 many workers considered them leeches placed Leidy's species 

 Astacobdella philadelphica (Leidy, 1851) in the European genus 

 Branchiobdella and described as new members of this genus B. 

 illuminata, B. pulcherrima, and B. instabilia. He quickly reassigned 

 B. illuminata, establishing the new genus Bdellodrilus for it in his 

 excellent treatment of its anatomy (Moore, 1895). Pierantoni (1912, 

 pp. 21-22), who realized that these species have two testicular seg- 

 ments, placed Branchiobdella pulcherrima and B. instabilia in Moore's 

 genus Bdellodrilus. It remained for Ellis (1919, pp. 243-253) to 

 establish the genera Xironogiton, in which he placed Bdellodrilus 

 instabilia, and Xironodrilus, which includes B. pulcherrima. Ellis, 

 however, did not have material that would allow him to deal with 

 Branchiobdella tetradonta (Pierantoni, 1906, p. 3) and B. americana 

 (Pierantoni, 1912, p. 14). The next important paper in which these 

 species were considered was written by Clarence J. Goodnight (1940), 

 who retained Pierantoni's generic assignments for them. Though he 

 had not seen anything he could identify as B. tetradonta, he did con- 

 sider animals from Cleveland, N.Y., taken from Cambarus bartonii 

 robustus (Goodnight, 1940, pp. 28-29) as representative of B. 

 americana. In the same paper (p. 55) he described the third species I 

 am dealing with here as Stephanodrilus obscurus. Stephanodrilus is a 

 junior synonym of Cirrodrilus Pierantoni (Yamaguchi, 1934, pp. 

 191-192), and Yamaguchi's error in ignoring the law of priority by 

 using Stephanodrilus as the name of the Asiatic species, all of which 

 he considered to be congeneric, was corrected by Goodnight (1940, 

 pp. 55, 63) by reverting to the use of both of the Pierantonian names 

 (Cirrodrilus and Stephanodrilus). For the present, basing the position 

 on Yamaguchi's descriptions, figures, and some Japanese material 

 that he very kindly gave me a few years ago, I accept his decision 



