TRUNCATELLA. 183 
Erpelometra Lowe mss. olim. *) 
Helicis sp. Pulteney. 
Turbinis sp. Montaqu. 
Cyclostomaltis. sp. Drap. etc. 
Acmeae sp. Hartm. olim. 
Paludinae sp. Payraudeau 
Pyramidis sp. Brown olim. 
Rissoae sp. Phil., Mich. 
Turritellae sp. Fleming. 
Genus testae formatione certe bene circumscriptum, 
emissis speciebus nonnullis a Cl. Philippi et C. B. Adams 
ob animalis similitudinem hue relatis, sed testa non turriculata 
nec truncata, et peristomate disjuncto, acuto discrepantibus, 
pro quibus anno 1841**) genus Paludinellam proposui. 
Omnium specierum testae juniores turriculatae et acuminatae 
sunt, e majore anfractuum numero constantes, quam in adultis 
sponte truncatis et materie testacea apice denuo clausis ob- 
servamus. 
Discrepantia inter Auctorum sententias de operculo, quod 
a plerisque 20m spiratum, a Cl. Gray autem spirale descri 
bitur, facile solvitur examine exactissimo operculi, quo nucleum 
distinctum basalem, vestigia lineae spiralis offerentem , obser- 
vamus, in figura Woodwardi luculentissime perspiciendum. 
Omnes species habitu persimili gaudent, imo species e 
terrae partibus remotissimis allatae interdum  europaeis tam 
similes sunt, ut primo aspectu identicae appareant, quamvis, 
ut in Succineis, characteres sufficientes ad separandas species 
examine minutiore plerumque erui possint. Attamen negari 
non potest, distinctionem specierum difficiliorem reddi, quia 
multae formae, in reliquis characteribus congruentes et locis 
lisdem viventes, testae sculpturam pervariabilem ostendunt, 
ita ut a testa laevigata omnes gradus ad fortiter striatam obser- 
vemus. Quare a forma aperturae et peristomatis, a convexi- 
tate anfractuum, nec non a crista basali, in aliis magis minusve 
conspicua, in alüs deficiente, characteres specifici praecipue 
derivandi sunt. 

*) It is now nearly three years since the acquisition of a single live 
specimen of Cyclostoma truncatulum Drap., and a long and continued 
observation of its animal, convinced me that it was entitled to rank as a 
distinct. genus from any which were then constituted. I had accordingly 
designated it in my MSS. by the generic name of Érpefometra, derived 
from its peculiar manner of crawling. (Lowe in Zool. Journ. V. p. 299.) 
**) Wiegm. Arch. f. Naturg. 1841. I. p. 227. Typus: 4elir httorina 
Delle Chiaje. 
