REPORT ON THE I.AMELLIBRANCHIATA. 145 



Tiiuseular impression is elongate and a little smaller than the posterior. The pallial 

 sinus has not been recoornised. 



Length 3 mm., height 2|, diameter 1^. 



Habitat. — Station 188, west of Cape York, North Australia, in 28 fathoms, green 

 mud ; and off the reefs at Honolulu, Sandwich Islands, in 40 fathoms. 



Since writing the above description, based ujinn two valves from Station 188, three 

 more valves from Honolulu have been forwarded to me which agree in every particular. 

 They are rather largi^r than the figured valve, being 3 J mm. long and 31- high. The 

 radiating granular ridges, which in the Cape York specimen extend only a short distance 

 from the sides, are produced almost to a central line down the middle of the valves, 

 where they divaricate. From the general aspect of those specimens 1 am rather inclined 

 to think that the species will ])rove permanently small, and possibly not much larger 

 than the above dimensions indicate. 



Circe arnica, n. sp. (PI. TT. figs. 2 -2e). 



Testa transversa, ovata- superne acuminata, paululum insequilatcralis, alba, ad mar- 

 ginem dorsalem utrinque rubro maculata, concentrice subcostata et sulcata, umbones 

 versus Isevigata, in sulcis et ad utraque latera radiatim lirata. Margo dorsi utriuque 

 subfequaliter dcclivis, postice levissime arcuatus, autice aliquanto concavus. Ventris 

 margo late curvatus, acute rotundatim in dorsalem anticam ambiens, cum postico obtuse 

 angulatim junctus. Umbones parvi, acuti, paulo ante medium collocati. Lunula 

 lanceolata, linea incisa circumdata, rubro tincta. Area angusta, subju-ofunda, marginilnis 

 subangulatis, postice rubro maculata. Dens medianus in utraque valva maguus, conicus, 

 anticus valvse dextrse eodem minor in valva sinistra. Cicatrices subprofundse, antica 

 parva, elongata, infra dentes laterales sita, postica latior. Sinus pallii medioeriter 

 latus, sed minime profundus. 



The shell of this species is a little inequilateral, the anterior side being rather 

 shorter than the j^osterior. It is entirely white, with the exception of a spcar-head- 

 shaped red spot on the front part of the lunule and a smaller spot of the same colour 

 on the hinder part of tiic posterior dorsal margin. It is considerably longer than high, 

 about equally broad at each end, rather finely radiately Urate down both sides, and 

 concentricallv ridged and grooved near the ventral margin, at the beaks and for a short 

 distance beneath them being almost smooth. The ridges are unequal in size, very little 

 elevated, and somewhat granulous at the sides, where they are crossed by the radiating 

 costellfe. The furrows too are shallow and unequal in width, and have a punctate 

 appearance which is caused by the presence of fine radiating lirse interrupted by the 

 concentric ridges. The dorsal margin descends about equally on each side, but whilst 



(ZOOL. CHALL. EXP. — PART .X.KXV. — 1885.) Mill 19 



