8 University of Michigan 



himself did not attempt to designate verrucosa as the type of 

 Pleurocera. If he had, the designation would have been in- 

 valid. Hannibal had no more right to designate as the type 

 a species that does not agree with the original generic specifi- 

 cations than Rafinesque had by erroneously including it in his 

 genus. In other words, he cannot, by such designation, validate 

 the erroneous action of Rafinesque in describing verrucosa as 

 a Pleurocera. 



If, on the other hand, my contention is erroneous, and the 

 third rule laid down in Opinion 46 is to be construed literally, 

 without reference to the remainder of the opinion and without 

 any qualification, then verrucosa became automatically the type 

 of Pleurocera and Hannibal's designation was only the state- 

 ment of a fact already .determined. 



III. 



If the preceding argument is correct, and verrucosa Raf. 

 is not available as the type of Pleurocera, its genotype still 

 remains to be determined. No other designation of a type for 

 the genus has ever been made, and, unless the question has 

 already been determined under the rules laid down in Opinion 

 46, the designation of a proper type is still open. 



But it seems to me that the question is already settled. 



In 1 83 1, Rafinesque described three additional species of 

 Pleurocera. Two of them from Kentucky are unidentifiable. 

 But the third, P. acuta, from I.ake Erie, is undoubtedly, as it 

 appears to me, the species from the Niagara River described 

 by Lea as Melauia subuhiris. 



Rafinesque's species has been referred to Goiiiobasis vir- 

 g'mlca Gmel. by Hannibal, but, as virginica is not known from, 

 the Lake Erie Basin and does not agree with the description 

 of acuta, the approximation is evidently erroneous. 



