56 PROCEEDINGS OF THE ACADEMY OF [Feb.,. 



Sphcerium sp. Lymnoea utahensis Call. 



Musculium n. sp. Planorhis trivolvis near hinneyi 

 Succinea rusticana Gld. Tryon. 



Valvata humeralis calif ornica Planorhis parvus Say. 



Pils. Planorhis exacuous Say. 



Lyjjmceastagnalisappressa&ay. Physaampullacea Gld. 



Lyynncea proxima Lea. Aplexa hypnorum (Linn.). 



The Planorhis trivolvis at all stations in this valley reaches great 

 size — up to 35 mm. in diameter in some instances. They have the 

 strong transverse sculpture of the variety hinneyi, but the whorls 

 are not quite so conspicuously strap-like as those from Sta. 127 at 

 Utah Lake. Caddis larvae cases from one of the sloughs are com- 

 posed almost wholly of Planorhis parvus, P. exacuous and other small 

 shells and shell fragments. Planorhis exacuous was described by 

 Say,^ in 1821, under this name as thus spelled, apparently a poorly 

 formed adjective from exacuo or from acuo, referring to the sharp 

 periphery. It should have been spelled either exacuus or exacutus. 

 Gould,'' in 1841, inserted the t, saying: 



"I cannot but think that the name under which this shell appears 

 in the 'Journal of the Academy,' is not exactly as it was intended by 

 the author, as it is neither a Latin word nor a Latin termination. 

 Supposing that by a typographical error, an o has taken the place 

 of a t, we have a legitimate term, and one very expressive of the 

 form of the shell." 



In his synonymy he gives the original spelling. Haldeman, in his 

 monograph, 1842, follows Gould, but in the synomany he also cites 

 the name as originally published. Unfortunately, Binney,^ in 1865, 

 adopting Gould's form of the name, in his synonymy of the species 

 cited Say's original description as though it had been spelled exacutus. 

 As the latter is the work most generally accessible and used for 

 reference, it has misled many subsequent writers. If the original 

 name were clearly a misprint and we could ascertain just what was 

 intended, the rules of nomenclature would justify its correction. 

 It is conceivably, though not likel}', a case of poor judgment in the 

 formation of the word, and not a typographical error. If a printer's 

 error, it seems more likely that the printer, well accustomed to the 

 common English syllable ous, had carelessly inserted an o in exacuus, 



« JouRX. Acad. Nat. Sci. Phila., II, p. 165, 1821. 



'A Report on the Invertebrata of ^Massachusetts, pp. 208-209, 1841. See 

 also Binney's edition of the same, pp. 49.5-496, 1870. 

 * Land and Fresh Water Shells of North America, Part II, p. 126. 



