23 



Theacia pusilla. T. minuta, rotimdato-OTata, flarescens, antice 

 late rotundata, postice trimcata (angulo dorsali recto) concentrice 

 exiliter undulata ; umbonibus vix postmedianis ; declivitate umbonali 

 angulata. Long. 8 ; alt. 5 ; lat. 4 millim. Inhabits Simoda. W. S. 



A little like T. myopsis, Beck, wbicb seems to be the same as Anat. 

 papyracea Say. 



Thracia cultrata. T. parA^a, alba, tenuissima, ovato-rhom- 

 boidea, ventricosa, intus argentata, antice semi-elliptic a late rotiuidata ; 

 umbonibus postmedianis acutis ; margine dorsali posteriori declivi, 

 extremitate truncata, angulo superiori acuto; declivitate umbonali 

 acuta ; margine ventrali vix arcuata ; apophysi cardinali triangulari 

 (valva sinistra ignota). Long. 8 ; alt. 6 ; lat. 4 millim. Inhabits 

 Port Jackson, sandy mud, 8-15 fathoms. W. S. 



Thracia coxcinna. T. parva, alba, transversa, antice rotundata, 

 postice truncata, convexiuscula, minutissime punctata ; umbonibus 

 postmedianis, declivitate umbonali angulata, valvis magnitudine et 

 convexitate satis discrepantibus : cardo debilis ; fissurd apicali pervia. 

 Long. 17; alt. 11 ; lat. 8 millim. Inhabits Kagosima Bay. W. S. 



Much like T. villosiuscula in outline, but more convex. 



Myodora fluctuosa. T. parva, tenuis, albida, umbonibus fere 

 medianis : valv. dextra convexa, postice triangularis, apice truncata, 

 undulis concentricis, circ. 20 ad margines haud protractis ornata ; 

 (valva sinistra ignota) : cardo debilis ; dentibus elongatis. Long. 8 ; 

 alt. 7 ; lat. 3 millim. Inhabits Kagosima Bay. W. S. 



Allied to M. brevis, which is larger and more finely ribbed. There 

 is one in the Cuming Coll. much like it. 



Lyonsia ventricosa. T. ovato-falcata, tenuis, fragilis, lucida, 

 straminea, ventricosa, concentrice exiliter striata et rugis hispidis 

 radiata ; umbonibus satis antemedianis ; extrem. antic a rotundata ; 

 extrem. postica angustante ad apicem truncata ; margine ventrali 

 lente arcuata ; cardine valdc debili. Long. 1 7 ; alt. 9 ; lat. 8 millim. 

 Inhabits Hakodadi Bay, 2-6 fathoms, sandy mud. AV. S. 



Its shorter and less slender form, and its color, distinguish it from 

 L. Norvegica and hyalina. 



Lyonsia (Pandorina) flabellata. T. oblongo-ovata, nasica, 

 ventricosa, tenuis, opalina, straminea, exilissime striata ; umbonibus ad 

 trientem anteriorem sitis ; extremitate antic a arete rotundata ; mar- 

 gine dorsali postica recta ; margine ventrali una cum extrem. postica 

 continue arcuata usque ad angulum superiorem: cardo debilis; sulco 

 ligamentali angusto ; pagina interiori opalina. Long. 17; alt. 10; 

 lat. 6 millim. Inhabits Arctic Ocean. W. S. 



Very close upon P. arenosa Moll., but the striaa are more numerous 

 and delicate. 



