159 



4. Monograph of the recent species of Trigonia, in- 

 cluding THE description OF A NEW SPECIES FROM THE 



Collection of H. Cuming, Esq. By Arthur Adams, 

 R.N., F.L.S. etc. 



(MoUusca, PI. III.) 



Trigonia, Bruguiere. 



Testa eequivalvis, incequilateralis, transversa, trigona, interdum 



suborbicularis ; dentes cardinales ohlongi, lateraliter com- 



pressi, divaricati ; duo in valvd alterd, utroque latere trans- 



versim sulcati ; quatuor in alterd, uno tantum latere sulcati; 



ligamentum externum, crassum, marginal e ; impressiones muscu- 



lares duce. 



Shell equivalve, mostly inequilateral, transverse, rather triangular, 



sometimes suborbicular ; cardinal teeth oblong, laterally compressed, 



divaricated, two in one valve transversely grooved on both sides, four 



in the other grooved on one side only ; ligament external, thick, rather 



short, marginal ; muscular impressions two. distinct, lateral ; palleal 



impression very nearly entire. 



Trigonia margaritacea, Lamarck. T. testd siiborhicidatd, 

 radiatim costatd, intus margaritaced, costis elevatis, verrucosis, 

 subasperis ; matgine plicato. 



Shell rather compressed, vdth 20 or 23 rather narrow, nodulose, 

 radiating ribs ; the hinder ribs very compressed, all excepting the 

 front ribs wide apart. 



Hab. Van Diemeu's Land ; Ronald Gunn, Esq. (Mus. Cum.) 



Trigonia margaritacea, Lamarck, Ann. du Mus. torn. iv. p. 355. 

 pi. 67. fig. 2. 



T. pectinata, Lamk. 



Trigonia Lamarckii, Gray. T. testd subventricosd, solidd, 

 costis 20-26 angustatis planiusculis nodulosis radiantibus, 

 costis areae postiece confertis angustatis, costis omnibus confer- 

 tis nodulosis. 

 Hab. in Nova Hollandia. 



Shell rather ventricose, solid, with 20 to 26 narrow, flat-topped, 

 nodulose radiating ribs ; the ribs of the hinder slope narrow, rather 

 crowded ; ribs convex, all close together and nodulose. 



Hab. New Holland, Port Jackson ; Mr. Stutchbury. (Mus. Cum.) 

 Varies, with the inside white, salmon-coloured, yellow, or purple 

 bronze. 



Trigonia Lamarckii, Gray, Annals of Nat. Hist. 1838, p. 482. 



Trigonia Jukesii, A. Adams, n. sp. T. testd ovato-trigond, 

 postice truncatd, margine sinuato, radiatim costatd, costis circa 

 20-24, elevatis, tubercidato-nodosis, tuberndis rotundatis, ob- 

 tusis, inargine venfrali valde pectinato. 



(MoUusca, PI. IIL figs. 4, 5, 6.) 



Shell ovately trigonal, posteriorly truncated, the margin sinuated. 



