REPORT ON THE LAMELLIBRANCHIATA. 71 



iiiclinati. Ligamentum Havum in sulco angusto marginali sitiim. Sinus pallii latus, 

 arcuatus, havid profiiudus. 



This species is ouly slightly inequivalve, equilateral, one-third longer than high, 

 moderately convex, ii-regularly triangular, narrowed in front and broadly truncated 

 posteriorly. The valves are white, very finely granulated throughout, exhibit marks of 

 growth at intervals, and have a rounded angle extending from the umbones to the lower 

 posterior extremity, and another subparallel with tlie margin which encloses the dorsal 

 area. The dorsal margin is rectilinear posteriorly and nearly so in front, and almost equally 

 obliijue on both sides, forming at the apex an angle of about 130°. The anterior end is 

 rather wedge-shaped and rounded at the extremity, the posterior side being squarely 

 truncated, forming rounded angles with the dorsal and ventral margins, the latter being 

 but very little curved and rather more ascending in front than behind. The external 

 ligament is yellowish, and located in a narrow marginal groove behind the beaks. 

 The pallial sinus is broad, arcuate, but not deep. The interior is not very glossy and 

 radiately substriated. 



Length 13 mm., height 9|, diameter 5. 



Habitat. — Station 162, off East Moncceur Island, Bass Strait, in 38 to 40 fathoms. 



This species is rather like Myodora australica, Reeve, in respect of form. 



T/iJ-acia modesta, Angas. 



Thracia modesta, Angas, Proc. Zool. Soc. Lond, 1867, p. 908, pi xliv. fig. 3. 

 Habitat. — Port Jackson, Sydney, in 2 to 10 fathoms. 



The left valve of this species is rather shallower than the right. The single valve 

 obtained by the Challenger has the posterior truncated end rather broader than the 

 type figured by Angas, and the lower outline less curved. 



Periploma, Schumacher. 



Feriploma compressa, d'Orbigny. 



Periploma compressa, d'Orbigny, Voy. Am^r. Merid., vol. v. p. 514, pi. Ixxviii. figs. 19, 20. 



Testa transversim ovata, antice late rotundata, postice angustior, breviter acuminata, 

 hians, paulo dextrorsum flexa, valde ingequilateralis, subcompressa, sordide, albida aspera, 

 minute grauulata, incrementi liueis striata. Margo dorsi anticus perelongatus, leviter 

 arcuatus et declivis, posticus longe brevior, magis obliquus, primo rectiusculus. Margo 

 ventris late curvatus, postice leviter sinuatus. Umbones parvi, acuti, fissi, circa in i 

 longitudinis coUocati. Ossiculum cardinis ovatum, costa oblic^ua sufFultum. Pagina 

 interna submargaritaeea, linea ai-cuata in valva sinistra ab umbone latum posticum versus 

 radiante notata. Sinus pallii breviter linguiformis ad apicem rotundatus. 



