INDEX. 
449 
Nephridia. and functions 1^0, Ano- 
doHtu 17S, 179, -iJ-', 333, A.cy(jnea, 
section 179, 334, A/jrioliinnx agrcs- 
tU, section 335, Helix loS, Succinca 
jintris, position 334, Helix arbus- 
forum, cellular .structure of 3.33. 
Xeritina fluviatiliji, incra.ssatioii 79, 
odontophore 264, odontophoral for- 
mula J'b’J, operculum 127, operculum 
in situ 124, otocyst 237, pseudo- 
striate muscle-fibre 141, sexual or- 
gans 353, unstriate muscle fibre 140. 
Nervous system, 137, 209, afferent 212, 
Anoclonta cygnea 216, of archetype 
142, basommatopbora 215, efferent 
212, eiithyneura 214, fibrils of 209, 
212, gastropoda 213, Helix aspersa 
147, 148, inhibitory 212, Limax 215, 
Limmm stagnalis 7, motor 212, 
nerve ring of Helix aspersa 149, 
pelecypoda 107, 168, 215, strepto- 
neura 213, stylommatophora 214, 
Succinca putris 215, sympathetic 
212, torsion of 221, Vivipara 7. 
Neurobranchiata S. 
Neuro-epithelial cell oi Arion ater 135. 
Nomenclature, principles of IS, oral 
folds in Clausilia 67, literature IS, 
of monstrosities 17. 
Norwich crag deposits 474- 
Nucleus of univalves .30, sculpture 72. 
Nucula, auditory canal 238. 
Nucula nuchus, reptaiy foot 195. 
Oblique aperture 33. 
Oblong bivalves 51. 
Ocelli (see Dorsal eyes). 
Odontoblasts 257. 
Odontognatha 234, 2-55. 
Odontophore 248, 250, 261, develoji- 
ment 2.57 . 258, function 248, growth 
153, Helix aspjersa 152, 261, 270, H. 
pygnuca 271, Hyalinia alliaria 264, 
H. nitidula 271. Ncritina Jluviatilis 
264, Physa fontinalis 268, Planorbis 
corncus 270, Testacclla halioticlea 
267, Vivipara vivqxira 265, notation 
of 262, transverse arrangement of 
’’ teeth upon 262. 
Odours, exhalation, perception of 229. 
Oisophagus 138, 172, 274, cells of 274, 
Helix aspersa 153. 
Olfactoiy organs 138, of archetype I42, 
224, sensory cells of 225, 226, Plan- 
orbis Cornells 225, in A nodonta 171, 
function and position 224, of Helix 
pomatia 130. 
Oligochromic colouring SO, pi. ii. , 
f. 10, 11. 
Oligocene, fossils 412, 413, strata 477. 
Ommatophores 187. 
Onchidium verruculatum, dorsal eyes 
234. 
(Jntogeuy 205, 378. 
22/12 1900 
Oolites, fossils of 498, strata 407. 
Operculata 7. 
Operculigerous lobe 193. 
Operculum 123, articulate 127, chemi- 
cal structure 124, concentric 126, 
Cydostoma clcgans 126, multispiral 
126, Xeritina Jluviatilis 127, peg .and 
rib of 124, 127, paucispiral 126, spiral 
725, subspiral 127, Vo.lvata piscinalis 
126, Vivipara contccta. 126. 
Opistliogyrate llo. 
Opisthobranchiata 8. 
Optic, bulb 233, sensory cellules 232. 
Oral, region 135, folds 08. 
Orbicular muscles of Anodonta 181. 
Organization, literature of 383. 
Organs of Bojamis (see Nephridia). 
tfriental region 398, pi. v. 
Ornamentation of bivalves 50. 
Orthostrophy 111. 
Orthoneuroid 222. 
Osborne beds 477. 
Osphradial (see Visceral ganglia). 
Osphradium 224, section in Planorbis 
Cornells 225, po.sition in Liinnaa 
peregra 228, cells of 210, 225. 
Otoconia 2.39, of enthyneura 239, 
Helix pomatia 151, 241. 
Otocysts 237, Anodonta. cygnca 170, 
Helix a.s])er.sa\5\, H. pomatia 151. 
Otoliths 239, Anodonta cygnca 170, 
Cyclo.stoma clcgans 240, Spkccriuvi 
corncuni 239, 241. 
Outer lip 32. 
Oval bivalves 51. 
Over-crowding, effects of 85. 
Oviduct of Helix 160, 101. 
Ovotestis, Helix aspersa 160, 358. If. 
hortensis, maturation of ova and 
spermatozoa in 377, L. peregra. 358. 
O VO viviparity 382. 
Ovum 141, 100, 370, ovarian ovum 377, 
maturation of 377. 
Oxygnatha 255. 
Pairing 372, 373, 374. 
Palatal, lip .32, plate 24S, 253, 256. 
Palwarctic region 400, pi. v. 
Palieozoic, fossils 405, 400, strata 404. 
Pallial, atrophy 203, extension 149, 
199, 202, eyes 2.30, 2.33, 2.34, fusion 
198, ganglia 220, line 50, 180, 181, 
muscles of Anodonta ISO, 181, re- 
gion 1.35. 
Pallium 145, 198. 
Parabranchia 220. 
I’arapodia 19.3. 
Parietal, ganglia I48, ^vall 32. 
Parieto-splanchnic (seeViscer.al ganglia) 
Parasites 4-77, commensals 423, ecto- 
parasites 423. endo-parasites 422. 
Parasitism of Un io 383. 
Patella, heart 291, eye 232. 
Patelliform univalve 25. 
D 2 
