Dendrotrochus (Santotrochus) eva subsp. eva eva (Pfeiffer 1854

Figures 33K, 35F, 41E, 42G–I

Material examined. Vanuatu: FMNH 175196 (two specimens dissected, one radula examined), Clems Hill, 17 km NW of Vila, Nfate, dense forest, alt. 240 m, 22 Nov. 1972, L. Price.

Description. External morphology: Shell of about 5.5 whorls, white, glossy, spire and apex raised. Protoconch smooth; teleoconch sculptured with strong radial growth lines. Whorl profile rounded above and below keeled periphery. Internal walls of early whorls complete; umbilicus open, very narrow U-shape. Animal (Figure 35F) light yellow-brown. Mantle laps and lobes absent. Sole of foot tripartite; caudal apparatus formed from curled up sole (Muratov’s 1999 helicarionid type); caudal horn medium size; caudal foss horizontal slit in tail.

Mantle cavity: As for family. Pigmentation of tiny white spots.

Digestive system: Oesophageal crop absent.

Genital system (Figures 33K, 41E): As for family. Free oviduct of medium length; internal longitudinal pilasters present. Bursa copulatrix inserted at junction of penis and free oviduct; duct of bursa copulatrix wide, distinguishable from bursa copulatrix, internally with irregular pustules. Vagina absent. Penis moderately long; epiphallus enters penis through short verge; penis internally smooth, one circular penis pilaster present, penial diverticulum absent. Penial sheath present, enclosing only penis; penis retractor muscle attached to epiphallus. Epiphallus much longer than penis, simple internally. Epiphallic retractor caecum absent; diverticulum at junction of epiphallus and vas deferens in the form of a short lime-sac (thin-walled, no axial filament). Spermatophore long soft-walled tube closed at both ends, with no sculpture.

Radula (Figure 42G–I): Relatively long and narrow. Central tooth absent from single radula examined; first two lateral teeth with small ectocones; mesocones lanceolate; shorter than tooth base. Lateral and marginal tooth fields distinguishable. Lateral teeth with endocone absent; ectocone equal in size to first lateral tooth ectocone; mesocone shorter than tooth base. Marginal teeth with endocones absent; ectocones approximately same length and breadth as mesocone, not subdivided into extra teeth. Radular formula (~104.19.1.19.~104) × 110 rows.

Remarks. The anatomy of the species examined here shows strong similarities to the type species of the subgenus Santotrochus, Dendrotrochus layardi (Hartman, 1889) (Schileyko 2002b). In particular, both species share the presence of a penial verge and a large circular penial pilaster (referred to as a stimulator by Schileyko 2002b).

Santotrochus includes 2–3 species and is limited to Vanuatu (Schileyko 2002b). Solem (1959) described Santotrochus as a subgenus of Dendrotrochus and this usage is followed in the current study, although Schileyko (2002b) raised it to generic rank.

The varying taxonomic placement of Dendrotrochus is outlined above (Family Trochomorphidae: Remarks).

Dendrotrochus eva eva grouped with trochomorphids Trochomorpha rubens and Videna planorbis in the phylogenetic analysis (Figures 1–3).