422 MOLLUSCA. 
ARTHEMIS LAMBATA (Gould). 
Testa tenuis, cordato-orbicularis, lenticularis, sordidé alba, radiatim 
tenuissimé striata et liris concinnis concentricis, postice laminosis in- 
sculpta ; apicibus sub-medianis elevatis, acutis, anteversis ; margine 
dorsali postico dechvi, vix arcuato: lunula profunda, lanceolato-cor- 
data: interior albida ; sinu siphonali obhquo, acuto ; cardine denti- 
bus tribus divergentibus in utraque valva. 
Arthemis lambata, GovutpD; Proceed. Boston Soc. Nat. Hist., iii. 
277. July 1850. Expedition Shells, 84. 
Suetx thin, lenticular, nearly circular, somewhat cordate, nearly 
equilateral, of a brownish-white colour, shining. Surface very finely 
grooved concentrically, some of the ridges rising into sharp lamine at 
the extremities; a faint granular appearance is also produced by mi- 
croscopic radiating strie; beaks a little anterior, elevated, acute, 
strongly antrorse, excavated in front, and having a deeply impressed, 
lanceolate, cordate lunule: anterior end somewhat compressed, regu- 
larly rounded; posterior end broader, more elevated, dorsal slope a 
little arcuate, rapidly declivous, tip not truncate: ventral margin nearly 
circular, a little oblique. Interior dingy white; margin simple; sipho- 
nal sinus diagonal, acutangular, deep. The hinge has three divergent 
lamellar teeth in each valve. 
Length one inch; height nine-tenths of an inch; breadth half an 
inch. 
Drawn up on the anchor at the Bay of Islands, New Zealand. 
Archer. 
A. lincta is more elevated, has the ridges about twice as large, is 
destitute of radiating stri, is more solid, and has the ligament mar- 
gin excavated and the siphonal sinus more slender and acute. It is 
rather larger in size. 
Figures 536, 536 a, lateral and dorsal views of the shell. 

