148 Miscellaneous. 



shown that, from their nervous system, it would be impossible to 

 leave them in the group of the Hirudines in which they had been 

 placed. The other new characters, observed by M. Blanchard, confirm 

 this opinion, and appear to show that the MalacobdellcB should con- 

 stitute a particular division, completely independent of the Annelides, 

 the Hirudines, and the Anevormesi (Trematodes planar is) . — Comptes 

 Rendus, Nov. 26, 1849. 



Monograph of the recent species q/^Trigonia, including the descrip- 

 tion of a new species from the Collection of H. Cuming, Esq. By 

 Arthur Adams, R.N., F.L.S. &c. 



Trigonia, Bruguiere. 



Testa eequivalvis, incequilateralis, transversa, trigona, interdum 



suborbicularis ; dentes cardinales oblongi, lateraliter com- 



pressi, divaricati ; duo in valvd alterf}, utroque latere trans- 



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



ligamentum externum, crassum, marginale ; 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, distmct, lateral ; palleal 



impression very nearly entire. 



Trigonia margaritacea, Lamarck. T. testd suborbiculatd, 

 radiatim costatd, intus margaritacea, 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. 

 pi. dj. fig. 2. 



T. pectinata, Lamk. 



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

 costis 20-26 angustatis planiusculis nodulosis radiantibus, 

 costis area posticce confertis angustatis, costis omnibus confer- 

 tis nodidosis. 

 Hab. in Nova HoUandia. 



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, 



