347 



of the lower valve, its dark frilled upper margin, and the few 

 denticles near the hinge are among its peculiarities. 



OsTREA DiscoiDEA. T. subcircularis, planulata, tenuis, pur- 

 purea : valva superior striis crebris albidis radiata ; valva infe- 

 rior major, radiatim plicoso-rugosa ; colore saturatiori : cavositas 

 parva, argentata, purpureo-marginata ; margine prope apicem 

 plicoso-crenulato. Long. 1^; lat. 2 poll. Hah. ? 



The characters of the single specimen of this delicate and 

 well-formed oyster are so diverse from all others, that notwith- 

 standing the usual inconstancy of form in this genus, I think it 

 may be safely pronounced new. The small, purple-striped West 

 India Oyster (O. Brasiliana) is similar to it. 



Terebratula caurina. T. parva, fusco-cinerea, transversa, 

 convexiuscula ; quincuncialiter punctata, costis angulatis ad 12 

 interdum bifurcatis radiata ; margine ventrali circulari, flexuoso ; 

 apice acuto, rectangular! ; lateribus rectilinearibus, incumbenti- 

 bus; rostro brevi, vix curvato ; foramine circulari, interrupto : 

 apophysis branchialis tenuissima, angustata. Long. ^ ; lat. ^^ ; 

 alt. \ poll. Hah. Paget Sound. 



T. australis is closely allied, but is more elongated and more 

 convex ; the beak is also elongated and the ribs are less promi- 

 nent. 



Terebratula Patagonica. T. parva, solidula, albida, ovato- 

 triangularis, sub-trilobata, quincuncialiter punctata : valva oper- 

 cularis plana : valva major convexa, sub-gibbosa, costis tribus 

 medianis et utrinque costis quinque divaricantibus ornata ; ros- 

 tro brevi, marginibus inflectis ; foramine magno, rotundato : 

 apophysis branchialis exilis. Long. 4 ; lat. |- ; alt. -|- poll. Hal. 

 Coast of Patagonia. 



A smaller and less transverse species than the preceding, and 

 the disposition of the ribs is quite different. It is also closely 

 related to T. australis^ but differs from it in the same respects. 



Terebratula pulvinata. T. tenuis, lenticularis, orbiculato- 

 trigona, albida, quincuncialiter punctata : valva minor convexa, 

 latior quam longa, marginibus lateralibus rectis : valva major 

 convexior, seque longa ac lata ; apice rectangulari, truncato, 

 lateribus incumbentibus ; foramine modico, circulari : apophysis 



