HORSLEY : PRESIDENTIAI. ADDRESS. 51 



last whorl ; vortex, i.e. a whirlpool, from the appearance of the very 

 flat whorls ; spirorbis, i.e. circular coil. Its var. ecarijiata has not the 

 faint keel of the type. Section Bnthyoiiiphalus — deep umbilicus — 

 contains only contortus, i.e. twisted up. Hippeiitis is a Greek word 

 and means a horseman and the connection of ideas is not patent. 

 Its s'pQCx&'sfontanus bears a name indicating its love of springs — and 

 watercress beds. Segmentiua was named from the nautilus-like septa 

 or divisions which are visible through the shell. 



The name Physa means in Greek a pair of bellows, or a blast from 

 the bellows. Aplecia seems to be the Greek for unplaited. Its 

 specific name hypnorum means inhabiting the moss Ilypman, which is 

 terrestrial. 



Now we come to the Prosobraiichia, meaning that the branchiffi, 

 or breathing apparatus, are in front of tlie heart. 1 he first family is 

 Pahidestrinidce, the marsh living shells. The species jenkhisi was 

 named after Mr. Jenkins, a working upholsterer at Greenwich, with 

 whom I sought and studied it in the Plumstead marshes in 1889. 

 Var. carif?ata has a marked keel in the centre of the whorls, but few 

 seem to have noticed that sometimes the keel bears bunches of spines 

 at equal distances. Ventrosa, i.e. with a belly. Tay!ori\s the species 

 differentiated by Mr. F. Taylor. Stag7ialis has a variety harleei 

 named by Jeffreys after his friend Mr. Barlee, a west country con- 

 chologist, and another var. ociona, so named from its having eight 

 whorls. The genus Pseudamnicola meaning False Amnicola. Anatiua 

 means belonging to ducks. 



Bithynia, Bithinia (Gray), Bythinia (Jeffreys) — which is the right 

 spelling ? If Bythinia, the author meant to derive it from a Greek 

 word denoting deep water — which it does not inhabit. But there is 

 little doubt that Leach named it after the province in Asia Minor. 

 The specific name tentaculata means having tentacles. Its var. pro- 

 diida is more produced and the var. excavata has a deeper suture. 

 The other species leachi was named by Sheppard after Dr. Leach. 



The family Viviparidce, i.e. producing young alive. The var, 

 efasciata has no bands and was named unicolor by Jeffreys. Cotitecta, 

 i.e., mouth covered with an operculum. 



The family Valvatidce was so named from the possession of a valve 

 or operculum. Valvata piscinalis gets its specific name from inhabit- 

 ing fish-ponds. Why atitiqua or ancient was considered a good name 

 for a variety by Sowerby I cannot find, possibly as found in Holocene 

 deposits. The other species cristata is so called from its having a 

 branchial plume like the crest of a helmet. 



The family Assemaididce — Jeffreys calls Assiminea "a ridiculous 

 name" and adds "the author ought to have borne in mind one of 



