1?I 



tice in angulum ohtusum desinente ; epidermide denticulatd, ad 

 aiigulum anticum subfoliaced, conspicud : long. 3*5, lat. 0*9, alt. 

 1 • poli. 

 Hab. ad Montem Christi. 



Found in holes in stones, pierced by Pholades? at low vvater. 

 Tiiis is a very remarkable species, decidedly appertaining to Mr. 

 Swainson's genus Byssoarca. Its liinge line is entirely posterior, 

 very straight, and the teetli are very numerous, very small, and much 

 iiilerrupted. — G. B. S. 



Byssoarca pacifica. Byss. testd oblongdj pallidu, brunneo varii 

 strigatd ; radiatim costatd ; medio coarctato, costis minoribus ; 

 umbonibus remotissimis ; Intere antico brevio?-e, superne aciimi- 

 nato, costis 'pleriimque majoribus, rugosis, margine ventrali de- 

 clivi ; latere postico maximo, postice emarginnto, carind obtusd 

 ex umbone ad marginėm ventralem decurrente ; ared ligamenti 

 maximd, marginibus latis ; margine ventrali hiatu byssi magno : 

 long. 4-, lat. ■-I-5, alt. 2-^ poli. 



Hab. ad Sanctam Elenam. 



Found on rocky ground, in from six to eigliteen fatlioms, adhering 

 to eacii other in large bunciies. — G. B. S. 



Byssoarca alternata. Byss. testd ohlongd,subcyUndraced,pal- 

 lide brunned, radiatim striaid, antice posticecue pro/unde sul- 

 catd ; latere antico brevissimo, superne obtuse angulato, infrh 

 rotundato ; postico elongato, costis duabiis validis ex umbone ad 

 marginėm ventralem pnsticam decurrentibus, costis posticis validis 

 rugosis ; dentibus marginalibus posticis alternantibus ; ared liga- 

 menti angustd, antice latiore : long. 1-4, lat. 0*7x alt- O'dpolĮ. ,. 

 Hab. in Columbia Occidentali. w i . / / > . .. ' -/.i 



Found attached to stones, on a rocky bottora, in tweTve fathoms. 

 —G. B. S. 



Byssoarca maculata. Bt/ss. testd oblongd, subrhomboided, ob- 

 liqud, decussatim striatd, pallidd ; ared posticd /usco-maculatd ; 

 latere antico parvo, superne angulato, latere postico longiore, su- 

 perne angulato, carind validd ex umbone ad marginėm hiferam et 

 posticam decurrente; ared ligamenti latd ; umbonibus incurvis : 

 long. 1-35, lat. 0-75, alt. 0-8 poli. 

 Hab. ad insulas Oceani Pacifici. 



Found attached to Motker-of-pearl Shells at Lord Hood's Island. 

 A thin pale-coloured epidermis covers the sbell^ vvhich is conspi- 

 cuous on the edge of the posterior ridge, where it forms lengthened 

 plumose setce. — G. B. S. 



Byssoarca MUTABiLis, Byss.testd oblongd, paUidhfuscd, decus- 

 satim striatd; latere antico plerumque breviore, nonnunguam 

 suhcequali, superne angulato, subttis rotundato ; postico longius- 

 culo, superne angulato, carind ex umbone ad marginėm inferam 

 et posticam decurrente ; ared posticd sukis majoribus decussatis : 

 long. 1-9, lat. 1-1, alt. 09 poli. 



