1888.] MOLLUSKS OF CHRISTMAS ISLAND. 537 



Descriptions of the new Species, 



ArIOPHAlNTA (VIlCROCYSns) NORMANI. 



Testa depressa, parva, anyuste perforata, tenuissima, nilida, sub- 



pellucida, olivaceo-cornea ; spira leviter conica, parum elevata ; 



anfractus 5—6, convexiusculi, lente crescentes, stitura marginata 



sejuncti, utrinque obsolete microscopice spiraliter striati, ultimas 



ad peripheriarn curvatus aut vix angulatus ; apertura parva, 



oblique semilunata ; peristoma tenue, margine columellari breviter 



dilatato. Diam. niaj. 6| millim., min. 6, alt. 4g. 



The form of this species seems to be somewhat variable, some 



specimens being considerably more elevated than others. The spiral 



striation is only visible mader the microscope, and even then appears 



very slight. 



A. perpolita, Mousson, from Tongatabu, A, mi/ops, Dohrn, a 

 Philippine form, and A. cicercula, Gould, from the Sandwich Islands, 

 are allied forms, but differ in various respects. 



Ariophanta (Microcystis) MABELiE. 



Testa A. normaiii simillima, sed mayis complanata, anfractibus 



fere planis, distinct ius striatis, ultimo ad peripheriarn angulato. 



Diam. maj. 6 millim,, min. b\, alt, 'i\. 



This species, it the specimens at hand be adult, seems to be a 



little smaller than the preceding. It is similarly perforated, of the 



same texture and glossy appearance, but is more depressed, has 



flatter whorls, wliich are a trifle more perceptibly spirally striated ; 



the body-whorl is quite angular, and consequently the form of the 



mouth is rather different. 



Ariophanta (Microcystis) mildrece. 



Testa A. normani similis, sed minor, latius perforata, anfractibus 



magis convexis, utrinque distincte spiraliter striatis. Diam. 



maj. 5 millim., min, 4j, alt, 3. 



This species is considerably smaller, but more widely perforated 



than either of the preceding species, and is also more strongly striated, 



the striae being visible under a simple lens. The suture is deeper 



than in either of the others and the whorls more convex, the last 



being well rounded at the periphery. All these three species are 



thin, semipellucid, and brownish or olivaceous horn-colour. 



/J ?. SUCCINEA LISTERI. 



Testa elongato-ovata, superne acuminata, tenuis, cornea, rubescens ; 

 anfractus tres, rapide crescentes, ultimus permagnus, incrementi 

 lineis tenuibus striatus ; apertura elongata, ocata, superne acu- 

 minata ; peristoma tenue, marginibus callo tenuissimo junctis. 

 Long, 13^ millim., diam. maj. 8; apertura \.0\ lonya, 7 lata. 

 This species differs in form, sculpture, and colour trom botii the 

 other species of the island. It is smoother, suffused with a reddish 

 vinous tint, and has a shorter spire aad a longer body-whorl. 



