147 



cularis, tenuis, fragilis, inaequilatera, lamellis concentricis con- 

 fertis, regularibus, - erectis, ad extremitatem anticain altio- 

 ribus sculpta, in interstitiis minute et dense radiatira striata, 

 opaca, squalide alba; iimbones antemediani, minimi, obliqui ; 

 margo dorsalis anticus brevissime concavus, tum aiigulo acuto 

 in anteriorem et ventralem, circuli segmentum reguläre for- 

 mantes abiens, posticiis parum convexus, declivis, angulo 

 obtuso terminatus; lunula ovato-acuminata,^ striata, impressa, 

 medio carinata; area in valva dextra suhnulla, in sinistra 

 angitsta, angulo liraitata; ligamentum immersum, vix con- 

 spicuum ; pagina interna albida, medio pallide isabellina; 

 pallii sinus magnus, triangulari-linguaeformis, antice subrotun- 

 datus, linea supera fere horizontali, infera subrecta, oblique 

 adscendente, antice sursum curvata; dentes cai'dinis mediocres, 

 in valva sinistra secundus subbifidus, cum primo tenui trian- 

 gulatim complicatus, lunularis appropinquatus, parum erectus. 

 — Long. 33, alt. 31, crass. 14 mill. — Habitat in Tasmania. 

 D. Trailli A. Adams in Proc. Zool. 8oc. Lond. 1855. 

 p. 223; H. et A. Adams Gen. II. p. 432; Römer Mon. 

 Dosin. p. 62. n. 71 (ex A. Adams). — T. suborbicularis, com- 

 pressiuscula, parum inaequilatera, solida, striis concentricis 

 elevatiusculis, alternatim prope extremitatem utramque eva- 

 nescentibus, reliquis lamellose incrassato-elevatis sculpta, vix 

 nitidula, pallidissiine fulvescenti-albida ; umbones parvuli, ni- 

 tidi, oblique involuti ; margo dorsalis anticus infra lunulam 

 subhorizontaliter productus, angulo obtuso in circuli segmen- 

 tum usque ad medium extremitatis posticae prolongatum abiens, 

 posticus leviter convexus, descendens, angulo obtuso termina- 

 tus; lunula oblongo-cordata, lamellosa, profunde circumscripta, 

 medio convexa ; area angusta, lanceolata, in valva sinistra 

 laevis, angido circumdata, in dextra lamellis fere ad rimam 

 ■productis munita, labio incumbente ; ligamentum conspicuuni, 

 immersum; pagina interna alba; sinus palliaris mediocris, sub- 

 triangulari - linguaoformis, antice attenuato - rotundatus, linear 

 supera subhorizontali^ concaviuscula, infera obliqua, leviter 

 convexa; cardinis dentes in valva sinistra secundus bifidus 



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