1888.] MOLLUSKS OF CHRISTMAS ISLAND. 537 



Descriptions of the new Species. 



Akiophanta (Microcystis) normani. 



Testa depressa, parva, anguste perforata, tenuissima, riilida, sub- 



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



anfractus 5-6, convexiusculi, lente crescentes, sutura marginata 



sejuncti, utrinque obsolete microscopice spiraliter striati, ultimus 



ad peripheriam curvatus aut vix angulatus ; apertura parva, 



oblique semilunata ; peristoma tenue, margine colamellari breviter 



dilatato. Diam. maj. 6| millim., min. (5, alt. 4^. 



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



specimens being considerably more elevated than others. The spiral 



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



very slight. 



A. perpolita, Mousson, from Tongatabu, A. myops, Dohrn, a 

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

 are allied forms, but differ in various respects. 



Ariophanta (Microcystis) mabel^. 



Testa A. normani simillima, sed magis complanata, anfractibus 



fere planis, disiinctius striatis, ultimo ad peripheriam angulato. 



Diam. maj. 6 millim., min. 5^, alt. 3^. 



This species, if 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 vphorls, which 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) mildred.e. 



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



magis convexis, utrinque distincte spiraliter striatis. Diam. 



maj. 5 millim., min. 4|, 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. 



ii 7rj SUCCINEA LISTERI. 



T'esta elongato-ovata, superne acuminata, tenuis, cornea, rubescens ; 

 anfractus ires, rapide crescentes, ultimus permagnus, incrementi 

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

 minata ; peristoma tenue, marginibus callo tenuissimo junctis. 

 Long. 13^ millim., diam. maj. 8; apertura 10^ longa, 7 lata. 

 This species differs in form, sculpture, and colour from botli the 

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

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



