159 
4. MoNnoGRAPH OF THE RECENT SPECIES OF TRIGONIA, IN- 
CLUDING THE DESCRIPTION OF A NEW SPECTES FROM THE 
Cotiection or H. Cumine, Esa. By Arruur ApDAms, 
R.N., F.L.S. etc. 
(Mollusca, Pl. IIT.) 
TriconiA, Bruguitre. 
Testa equivalvis, inequilateralis, transversa, trigona, interdum 
suborbicularis ; dentes cardinales oblongi, lateraliter com- 
pressi, divaricati; duo in valvd alterd, utroque latere trans- 
versim sulcati; quatuor in alterd, uno tantum latere sulcati ; 
ligamentum externum, crassum, marginale ; impressiones muscu- 
lares due. 
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. IT. testd suborbiculatd, 
radiatim costatd, intus margaritaced, costis elevatis, verrucosis, 
subasperis ; margine plicato. 
Shell rather compressed, with 20 or 23 rather narrow, nodulose, 
radiating ribs; the hinder ribs very compressed, all excepting the 
front ribs wide apart. 
Hab. Van Diemen’s Land; Ronald Gunn, Esq. (Mus. Cum.) 
Trigonia margaritacea, Lamarck, Ann. du Mus. tom. iv. p. 355. 
pl. 67. fig. 2. 
T. pectinata, Lamk. 
Triconta Lamarckil, Gray. T. testd subventricosd, solidd, 
costis 20-26 angustatis planiusculis nodulosis radiantibus, 
costis aree postice 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. 
Triconia Jukes, A. Adams, n. sp. 7. testd ovato-trigond, 
posticé truncatd, margine sinuato, radiatim costatd, costis circa 
20-24, elevatis, tuberculato-nodosis, tuberculis rotundatis, ob- 
tusis, margine ventrali valde pectinato. 
(Mollusea, Pl. III. figs. 4, 5, 6.) 
Shell ovately trigonal, posteriorly truncated, the margin sinuated, 
