4 University of Michigan 



5. In 1S64, ( Pr. A. N. S. P., p. 24), Tryon in his "Synop- 

 sis of the Strepomatid?e" revived the use of Pleurocera. His 

 reasons for so doing were given at length in the Am. Jour, of 

 Con., I, 1865, p. 97 et seq. This article was reprinted as the 

 introduction to his "Strepomatidge," Part IV, L. & F. W. Shells, 

 published by the Smithsonian Institution in 1873. 



6. In 1865, Binney (L. & F. W. Sh., Pt. Ill, p. 62, fig. 

 126) published a fac-simile of a figure of Pleurocera taken from 

 Rafinesque's unpublished 'Conchologia Ohioensis," which is 

 consequently available for nomenclatorial purposes from 

 that time. 



7. In 1912, Hannibal ( Proc. Mai. Soc. Loud., X, p. 169) 

 designated Pleurocera z'crmcosa Raf. as the generic type. 



8. In 1917, Pilsbry (1. c, ]). 110) accepted and adopted 

 Hannibal's designation. 



Argument. 

 I. 



It is to be noted that Kafinesque's original description of 

 Pleurocera in 1818, with six named, but undescribed, species, 

 and his revised diagnosis in 1819, with no species mentioned, 

 were both published before he described his Pleurocera verru- 

 cosa in 1820. Pleurocera was, therefore, a genus without a 

 type and the question at issue is : — what species under the facts 

 and a proper construction of the Code must be held to be the 

 genotype. 



Both of Rafinesque's generic descriptions taken by them- 

 selves, are adequate, "clearly giving generic characters,'' and 

 there can be no doubt but that Pleurocera was intended to 

 include the group of species, which for over fifty years has 

 been universally designated by that name. This is confirmed 

 by his figure, published by Binney in 1865 and since that time 



