SNAILS  Class GASTROPODA

Includes all of those mollusks commonly called snails and having (usually) a shell which grows spirally, expanding as the animal grows. Characteristics of the shell, such as pattern, color, presence of threads, grooves, teeth, etc., are very useful in the identification of marine and estuarine gastropods, but less so for freshwater species, many of which have thin, rather plain shells. For this reason, the following key sometimes must utilize soft parts that would not be observed in a shell collection. It is recommended to observe living animals whenever possible while attempting this key. A listing of the gastropod mollusks found in Hawaiian fresh and brackish waters is provided in CPIE.

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	40a	(33)	Shell cap-like or limpet-like, cone-shaped, or otherwise without conspicuous coiling	[41]
	40b		Shell conspicuously coiled: high-spired to bulbous, or coiling in one plane (discoidal or disk-shaped)	[43]
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	41a	(40)	Shell coiled, but spire incorporated into an enlarged body whorl (most recently formed full coil containing head and foot of withdrawn animal) and just visible laterally; concave underside of shell with shelf behind aperture (opening)	[45]
	41b		Coiling of shell not evident except possibly for the small, coiled cap at apex. Limpets (like an opihi)	[42]
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	42a	(41)	Shell a round or oval cap with strong radial grooves	[Note B]
	42b		Small (2-6 mm), somewhat flattened limpet with fragile, yellow to brown shell, without strong radial threads or grooves. On leaf litter or rocks in streams. Shell apex (peak) behind and to right of center of shell ~ Family ANCYLIDAE Ferrissia (Pettancylus) sharpi (Sykes)
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	43a	(42)	Shell neritiform: globose or flattened, with spire encased in body whorl and usually visible only along posterior, right side (but hardly or not at all projecting above an enlarged body whorl), and aperture with inner lip shelf-like	[45]
	43b		Shell high or low-spired, but spire projecting above (or behind) body whorl; OR shell coiling in one plane, forming a disk. Inner margin of aperture lacking a projecting shelf	[44]
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	44a	(43)	Shell high-spired, elongate: width less than 0.5 length. Mantle edge with papillae (soft projections). { Fresh or brackish water ~ Family THIARIDAE	[52]
	44b		Shell not high-spired; either globose, conical, or discoidal	[53]
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	45a	(41) & (43)	Snail lacking an operculum. { Freshwater only ~ Subclass PULMONATA, Family LYMNAEIDAE	[46]
	45b		Snail with conspicuous, calcareous operculum. { Marine, brackish, or freshwater ~ Subclass PROSOBRANCHIA, Family NERITIDAE	[47]
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	46a	(45)	Spire present but very short. Aperture about three-fourths of shell length. Inner lip lacking a callus. Freshwater; rare [end] Erinnia aulacospira (Ancey)	[Note A]
	46b		Spire entirely reduced. Aperture nearly as long as shell. Inner lip with a callus. Freshwater; very rare [end; Listed T] Erinnia newcombi (H. & A. Adams)	[Note A]
			   Key to Family Neritidae
	47a	(45)	Shell somewhat flattened, with lateral prolongations or "wings" and broad columella (shelf forming inner lip). Operculum with reddish, membranous, lateral fringe on exterior margin. Fresh or brackish waters	[48]
	47b		Typical globose, neritiform shell, usually not or only a little depressed (flattened) and lacking wing-like projections. Operculum without membranous fringe. Brackish to marine waters	[50]
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	48a	(47)	Operculum upper apophysis short and stout and joined to thick, triangular lower peg; outer face may be granulated, with a groove parallel to margin across the middle Clithon spp.	[49]
	48b		Shell thin-walled and gray, light purple, or olive-brown, smooth except for fine growth lines; prominently winged but longer than wide to 30 mm long; usually in estuary or mouth of stream. Hapawai Neritina vespertina (Sowerby)
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	49a	(48)	Shell moderately thick, dark gray to black, smooth with white speckles; inner lip with irregular, fine teeth; shell to 20 mm long but broader than long. Euryhaline and found mostly in brackish pools Clithon cariosa (Wood)
	49b		Shell moderately thick, dark or black, covered by low, rounded tubercles (juveniles and adults living at high elevations may have smooth shells), to 42 mm and about as broad or slightly broader than long; inner lip lacking teeth. Operculum a dark, red-brown. Fresh water, in flowing streams to 400 m elevation. Hihiwai or wi Clithon granosa (Sowerby)
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	50a	(47)	Shell mostly or entirely black with white speckles or spiral grooves	[51]
	50b		Shell ovate, smooth, yellow-brown to 2 or 3 mm. Found in brackish water tide pools and anchialine ponds. Rare Neritilia hawaiiensis Kay
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	51a	(50)	Shell globose to depressed, black with fine white speckles; inner lip with a middle area of fine teeth. Marine or brackish, but where marine, associated with fresh or brackish water springs at the shore and always immersed (subtidal). Pipipi Theodoxus neglectus (Pease)
	51b		Shell globose, never flattened, black with fine spiral grooves, to 14 mm. Marine, but supra-littoral (staying above the intertidal water line). Pipipi Nerita picea (Recluz)	[Note B]
			   Key to Family Thiaridae
	Melanoides tuberculata -- Kawa Stream, Kane‘ōhe
	52a	(44)	Shell sculptured with vertical, weakly curved ribs and much finer spiral striations; suture simple, not crenulated. Shell color brown or light-colored with red-brown dashes. Attains a length of 30-36 mm Melanoides tuberculata (Müller)
	52b		Shell sculptured with prominent nodes overlapping suture and forming crenulations. Base of last whorl with prominent spiral ridges. Shell more or less even brown, never mottled with reddish spots, 20-27 mm long, about 0.38-0.41 times as wide as high. Sides of spire concave in outline. Euryhaline Tarebia granifera Lam.

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Note A:
Although your identification may be correct, the species you arrived at is either rare or of limited or uncertain distribution in Hawai`i. Carefully compare the descriptions in the key with your specimen or observation and reconsider choices made in last few couplets to insure that a rare species is not being mistaken for a more common species.

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Note B:
Your identification is leading to a group with no fresh or brackish water representatives in Hawai`i. The identification may be correct for the location where you made the collection or observation (e.g., near the ocean), but the species is marine and may not be covered in the key. If the collection was made in freshwater, you should back up several couplets and confirm your decisions.