Botanical Society oj Edinburgh. 151 



Ter. Neapolitana given both by Scacdii, Phili})pi, and Kiister, do 

 not represent the characters of the species under notice, — so much 

 so that I beheved it new, and gave to it the name oiArgiope Forbesii^ 

 which must now be considered only a synonym : and Sowerby's 

 figure correctly illustrates the species. 



11. Rhynchonella nigricans, Sow. sp. 1846. 



Diagnosis. — Shell inequivalve, irregularly tetrahedral, wider than 

 long ; beak acute, and slightly recurved ; foramen not entirely sur- 

 rounded by the deltidial plates, a portion being completed by the 

 umbo ; beak-ridges well defined, leaving between them and the hinge- 

 line a false area, not indenting much the smaller valve ; surface orna- 

 mented by a variable number of sharp plaits, about twenty-five on 

 each valve, a few of which are due to intercalation ; mesial fold not 

 prominent, but defined, with a corresponding shallow sinus in the 

 larger valve ; apophysary system consisting of two short curved 

 lamellae ; colour bluish black ; structure impunctate. Length 8, 

 width 9, depth 4 lines. 



Hab. Five miles east of Ruapuke Island, New Zealand; dredged 

 by Mr. Evans, R.N., in 19 fathoms off coral and rock. Coll. Cuming. 



Obs. — When Sowerby described this interesting shell, only one 

 small young specimen, without locality, was known ; since then Mr. 

 Evans has dredged several, some of which exceeded the dimensions 

 above given. I therefore thought it advisable to redescribe the spe- 

 cies, more especially as it is scarcely distinguishable from half- 

 grown specimens of R. concinna^ Sow. 



12. Orbicula Evansii, Dav. 1852. 



Diagnosis. — Shell irregularly circular, nearly as wide as long, very 

 thick ; both valves almost equally orbicular or suborbicular ; apex 

 subcentral ; the unattached valve is ornamented by numerous strong, 

 radiating, elevated striae, which augment rapidly by the intercalation 

 of numerous smaller costae at variable distances from the apex ; these 

 are intersected by numerous concentric laminae of growth ; attached 

 valve very deep ; disk of adhesion small, almost central ; fissure mi- 

 nute, elongated ; surface covered by concentric raised laminae, with 

 longitudinal striae all round and near the edge ; colour yellow ; texture 

 horny. Length 5y, width 6, depth 4 lines. 



Hab. Bodegas. Coll. Cuming. 



Obs. — Mr. Cuming has three specimens of this Orbicula, all similar 

 in appearance, and distinguishable from O. Cumingii and O. strigata 

 by the great convexity of the attached valve, which is flat in the two 

 above-mentioned species ; the disk of adhesion is likewise much 

 smaller in O. Fvansii, and the striation stronger. 



BOTANICAL SOCIETY OF EDINBURGH. 



May 11, 1854. — Professor Balfour, President, in the Chair. 



Dr. Greville mentioned that he had been in correspondence with 

 INIr. Wilson upon the subject of the Nortli Uist Moss, which had 

 been referred by that gentleman to Leucodon LaguruSy while he him- 



