Zoological Society, fi9 



incurvatis ; pube pland ; dentibus lateralibus approximatis . Long. 

 1-30; lat. 1-60 pol. 

 Hab. Tumbez, Peru (Cuming). 



Closely resembling dentiferus, but not provided with the charac- 

 teristic tooth, much stronger and more triangular, and with its ven- 

 tral edge more arcuated, and its front extremity more attenuated. 

 The front dorsal edge appears retuse (which it is not in reality), from 

 the lateral projection of the swollen beaks. The lower margin is 

 stained with violet anteriorly. 



DonaxNavicula. Don. testd elongato-trigond, crassd, subventri- 

 cosd, nitidd, subineBquilaferali, sublcevigatd (striis radiantibus 

 tantum in medio perspicuis), albd, epidermide flavd indutd, prope 

 marginem dorsalem utrinque brunneo-purpurascente strigatd; mar' 

 gine ventrali in medio ventricoso, intus crenato ; dorsali antich 

 subrecto et subdeclivi, postice incurvato et declivi; ared posticd 

 Icevi, subconcavd ; latere antico longiore, angustato^ ad extremitatem 

 rotundato ; postico cuneiformi, ad extremitatem obtuso ; ligamento 

 minimo ; costd umbonali obtusd ; sUperficie internd albidd, utrinque 

 superne purpured ; dentibus lateralibus maxime approximatis. 

 Long. 0-40; lat. 0-90 poll. 

 Hab. Gulf of Nicoya, Central America (Cuming). 

 Allied to calif orniensis, but more triangular. 



DoNAx GRACILIS. Don. testd elongatd, angustd, nitidd, valdh in- 

 (Bquilaterali, compressd, sublavigatd, albidd aut pallide violaceO' 

 rufescente, epidermide lutescente indutd ; margine ventrali convcxo 

 aut subarcuato, haudflexuoso, intus crenulato ; dorsali magis mi- 

 nusve livido, utrinque subrecto, antice vix paululUm declivi, postice 

 valde declivi; latere antico producio, attenuato, ad extremitatem 

 rotundato, postico acuminate -cuneiformi ; ligamento minimo ; ared 

 posticd Icevi, obtusissimd ; costd umbonali obtusd ; superficie internd 

 purpurascente ; dentibus lateralibus perspicuis, approximatis. 



Var. b. Testd aVbidd^ radiis paucis livido^rufescentibus ornatd. 



Var. c. Testd rufescente aut lividd. 



Long. 0-40 ; lat. 1 poll. 



Hab. Bay of Guayaquil. Var. b. Chiriqui. Var. c. Bay of Garac- 

 cas (Cuming). 



Allied to Owenii, but with the margin crenulated. 



DoNAX soRDiDus. Don. testd abbreviato-cuneiformi, convexd, niti- 

 diusculd, solidd, valde incequilaterali, striis exilibus simplicibus 

 confertim radiatd, sordide albidd ; lineis elevatis obtiquis subcon- 

 centricis, partem superiorem et Icevigatam testa postice asperanti- 

 bus; margine ventrali crenulato, medio arcuato ; dorsali antico, 

 declivi et subrecto ; postico subrecto et valde declivi ; latere antico 

 attenuato ; postico brevi et inferne (in adultis etiam superne) obtitsh 

 angulato ; pube fortiter et confertim rugis subdecussatis concentrice 

 exaratd; costd umbonali subangulatd; superficie internd albidd, 

 purpureo infectd; dentibus lateralibus approximatis, antico per- 

 magno. Long. 070; lat. 1 poll. 



Hab. Cape of Good Hope. Mus. Brit., Cuming. 



