BIVALVES. SPONDYLUS. 45 



Virens — Greenish. Diaphana — Diaphanous. 



Maculosa — Spotted. Dura — Hard. 



Costata — Ribbed. Eburnea — Ivory. 



Wauaria — W-marked. Lucida — Pale. 



Tumens — Tumid. Discors — Confused. 



Aculeata — Acute ribbed. 



C. Ovate, a little angular near the beaks. 



*Literata — Camp lettered. Cruentata — Red-spotted. 



*Geographica — Reticulated. Lutescens — Charactered. 



Rotundata — Ovate. Sanguinolenta — Blood-spotted 



*Decussata — Intersected. Argentea — Silvery. 



Virginea — Modest. Donacina — Donax-formed. 



Virginica — Virginia. Afra — African. 



♦Rhomboides — Rhomboidal. Dealbata — Dead-white. 



Lithophaga — Stone-eater. 



SPONDYLUS. — Thorny Oyster or x\rtichoke- 



HEAD. 



Animal — a Tethys: Shell hardy solid, with unequal 

 valves: one of the valves convex, the other rather flat: 

 hinge with tivo recurved teeth separated hy a small 

 hollow. 



This genus, though containing innumerable varieties, 

 is divided into no more than ten species, and even these, 

 from their extreme irregularity of formation and great 

 similarity of appearance, may often be confounded 

 with each other. However, the most striking character 



