29 



than shelly) resembles lliat of Anomia, does not perforate the lower 

 valve directly, but is inserted betvveen the laminęs of the internal 

 fiurface of the lovver valve above the muscular impression and below 

 the hinge, and passes out into an external irregular somevvhat lon- 

 gitudinal superficial fissure or cicatrix, vvhich is narrowest at the 

 hinge margin, and which it entirely filis to a level with the sur- 

 rounding surface of the shell. 



Placunanomia Cumingii, Plac. testd subrotundatd, obscuri 

 argenteo.albidd, complanatd ; margine plicato, pUcis maxmis : 

 long. 2-į, lat. -rV> aii- 2 į poli. 

 Hab. ad oras Americae Centralis. (Gulf of Dulce, Province of 



Costa Rico.) 

 Dredged from a muddy bottom, at a depth of eleven fathoms, 

 attached to dead bivalve shells and dead coral. — W. J. B. 

 Genus Dentalium. 

 Dentalium splendidum. Dent. testd tenui, politd, basi carned, 

 apice majori lacted ; aperiurd posticd Jissuris duabus, alterd dor- 

 sali, alterd ventrali : long. l-i\, lat. -f\ poli. 

 Hab. ad oras AmericEe Meridionalis. (Xipixapi, West Columbia.) 

 Dredged in frora ten to sixteen fathoms water, on a sandy muddy 

 bottom. — G. B. S. 



Dentalium tesseragonum. Dent. testd tenui, lacted, l^vi, 



prbnum tetragond, ob angulos evanescentes dein cyliridricd ; lineis 



incrementi tenuissimis annulos subhyalinos ęffbrmantibus : long. 



A, lat. -rV poli. _ 



Hab. ad oras Americae Centralis. (Gulf of Nocoiyo and Puerto 



Portreroj also Xipixapi.) 

 Var. angulis indistinctis ; lineis incrementi annulos efformantjbus. 

 Obtained in the šame raanner as the preceding species.— G. B. S. 

 Dentalium ciuadrangulare. Dent. testd parvuld, albd, qua- 

 drangulari, angulis acutiusculis, interstitiis striatis ; aperturd 

 tetragond: long. -^, lat. -j^^ poli. 

 Hab. ad oras Americae Meridionalis. (Xipixapi.) 

 The colour of this shell is variable, being either milk-white, yel- 

 lowish, or reddish ; the angles are less acute at the larger end; and 

 at the smaller end there is sometimes forined a tubular appendage. 

 —G. B. S. 



Dentalium perpusillum. Dent. testd minima, tenui, angusta, 

 curvd, politd, albd ; apice acuto ; aperturd coarctatd, obliqud : 

 long. -tV, lat. -sV poli. 

 Hab. ad oras Americae Meridionalis. (Puerto Salango, West Co- 

 lumbia.) 

 This is related to Dent. Gadus, but is much more slender, and 

 the aperture is obliquely truncated from the dorsal to the ventral 

 margin. — G. B. S. 



Genus Helix. 

 Helix Monile. Hel. testd globosd, turgido-pland, translucidd, 

 corned, superne maculis strigisąue angidaiis moniliformibus or- 

 natd ; spira excavatd ; umbilico magno : long. y\, lat. \ poli. 



