REPOllT ON THE LAJlELLIBltANCHlATA. 151 



Dosinia lamhata (Gould). 



Arthemis lamhata, Goiiltl, Wilkes' Explor. Exped., vol. xii. p. 422, figs. 536-536a; Otia 



Conchol., p. 84. 

 Artemis lamhata, Hutton, Manual X. Zeal. Moll., p. 1,50. 



Testa subcircularis, superue producta, mediocriter teuui.s, nitida, alba vt-l lutesceiis, 

 insequilateralis, tenuissime concentrice striata, interstitiis ad latera quam in medio magis 

 elevatis, radiatim microscopice striata. Lunula parva, depressa, in medio paulo 

 prominens, acute cordata. Area postica inconspicua, angusta, baud profunda, marginibus 

 rotundatis limitata. Umbones prominentes, aliquanto incurvati, circiter in f longitudinis 

 locati. JNIargo dorsi anticus valde descendens, excavatus, lunula indentatus, posticus 

 minus descendens, leviter arcuatus. Cardo mediocriter levis, dente postico valvse dextrse 

 elongato, gracili, ad apicem fisso. Sinus pallii elongatus, adscendens, vix ultra medium 

 valvarum productus, ad apicem obtusus. 



This species is as high as long, rather circular, produced above at the l)eak.s, moderately 

 convex, inequilateral, glossy, dirty white, creamy white or pale yellowish-brown, marked 

 with excessively tine concentric striae, near the umbones scarcely visible to the naked eye, 

 all of which do not reach the dorsal margin, so that the interstices at the sides (especially 

 posteriorly) are broader, more elevated, and conspicuous than those on the central portion 

 of the valves. These are rather thin, and sculptured by numerous faintly impressed 

 radiating lines or substrise and also by countless other strite which cannot be seen except 

 with the aid of a microscope. The vimbones are somewhat produced, acute, curved over 

 a little at the apex and located far towards the anterior end. The ventral outline is 

 semicircularly arcuate, joins the hinder dorsal slope in a very faint rounded angle, and 

 runs into the anterior or lunular margin in a sharpish curve. The posterior dorsal 

 margin is a little convex, somewhat oblique, and much longer than the anterior side, which 

 descends rather abruptly and is concave, indented or irregular on account of the lunule. 

 The hinge-plate is not very thick, having the posterior tooth in the right valve elongate, 

 thin and grooved at the top, the central one in the left in young shells deeply cleft, and 

 the anterior lateral tooth very small, or almost obsolete. The anterior scar is long and 

 narrow, the posterior rather broader. The pallial sinus is deep, narrowly triangular, sub- 

 acute at the apex and produced upwards a little beyond the centre of the valves. The 

 ligament is visible externally, but a little sunken below the dorsal line. The lunule is 

 very small, elongate heart-shaped, sunken at the sides, and elevated along the central 

 line. 



Length 37 mm., height 3G, diameter 20. 



Habitat. — Station 167a, Queen Charlotte Sound, Cook Strait, New Zealand, in 10 

 fathoms, mud. " North Island only" (Hutton). 



This species is remarkaljle for the excessive fineness of the concentric sculpture and 



