48 PROCEEDINGS OF THE MA.LA.COLOGICAL SOCIETY. 



Section Paraspira, Dall, nov. sect. 

 Shell resembling Diplodiscus, but with the whorls rounded through- 

 out and the aperture simple, hardly expanded. Type, P. rstundatus, 

 Poiret. 



It may be noted that in order to use Diplodiscus, Westerlund, 

 Dr. Dall has a wholesome disregard for the rules of nomenclature, 

 which is indeed noteworthy after the priority purist view that he has 

 taken with regard to Euconulus fulvus, Miill. Dr. Dall is unfortunate 

 in his choice of a type species for his proposed section Paraspira, for 

 it is now quite impossible to say what Poiret's species was. 



It is sometimes applied to P. leucostoma, Millet, a form which is 

 so closely allied to P. spirorhis, Miill., that it is considered by some 

 authorities to be only a variety of that species, but this form some- 

 times possesses, if not a keel, certainly an angulation. Taking, how- 

 ever, the description of the section, the species which answers best to 

 the description is P. spirorbis, Miill., but in any case the only character 

 that separates the two sections is that Diplodiscus possesses a keel and 

 Paraspira does not. 



But this is not even a specific distinction in Planorhis, for it is an 

 inconstant character in P. albus, and cannot be considered sectional 

 even if we have a classification of only one species to each section. 

 A classific.ition which, purely on conchological grounds, places 

 P. spirorbis, Miill., in one section, and P. vortex, Linn., in another, 

 appears to me to be over- elaborate. 



Witii regard to another proposed section, larquis, and the subgenus 

 Gyraulus, Agassiz, there is a little confusion. Dr. Dall defines them 

 as follows : — 



Subgenus Gyraulus, Agassiz, 



Shell small, flattish, with few, rapidly increasing whorls, fully 

 exposed above and below with a nearly median periphery, spirally 

 striate and hispid ; aperture simple, sharp-edged, oblique. Type, 

 Planorbis albus, Miill. 



Section Torquis, Dall, nov. sect. 



Like Gyraulus, s.s., but with more rounded, less rapidly increasing 

 whorls, not hispid or spirally striate, the aperture expanded and 

 slightly thickened in the adult. Type, P. parvus. Say. 



The differences between the subgenus Gyraulus and the section 

 Torquis are so slight that they cannot be considered sectional. The 

 only real criterion is the presence or absence of spiral striae, and since 

 as a rule these can only be detected by the aid of a lens, I venture to 

 think that here again an unnecessary section has been created, and the 

 synonymy has been added to. Even Dr. Dall himself is not clear as 

 to the limits of this new section, for in the account of ^^ Planorbis 

 {Torquis) NathorsU, Westerlund," he states that it has spiral striation, 

 whilst in his definition of the section Torquis he expressly states that 

 it is not spirally striate. Moreover, he is of opinion that this species 



