LAMELLIBRANCHIATA, 79 



LITHODOMUS. 



Oblong, cylindrical, extremities rounded, covered with a thick 

 epidermis ; hinge linear without teeth ; ligament marginal, internal ; 

 interior nacreous ; boring in stonea. 



Warm and tropical seas. 



104. L. tmnCatUS, Gray, Dieff. N.Z., ii., p. 259. Contracted 

 in the middle, and rather tapering behind ; umbones rather prominent, 

 inflexed ; dark brown, inside purplish. Height, '5 ; length, 1'5. 



* 105. L. grilUGri, PMlippi. Shell acutely elongated, peculiarly 

 angularly gibbous about the umbones, attenuated anteriorly ; dark 

 chestnut, obliquely flexuosely furrowed throughout. {Reeve.) 



FAMILY AYICTTLID.E. 



Sub-inequivalve, oblique, resting on the smaller or right valve, and 

 attached by a byssus ; interior nacreous ; often eared, hinge line 

 straight, cartilage in one or several grooves. 



PINNA. 



Equivalve, wedge-shaped ; umbones quite anterior ; posterior end 

 truncated and gaping ; ligament groove linear, elongated. 

 Europe. North America. Panama. Australia. Pacific. 



106. P. zealandica, Gray, Dief. N.Z., ii., p. 259. Triangular, 

 elongate ; brown ; inside purplish ; valves convex, with rather close 

 obsolete longitudinal ribs, armed with close short semi-cylindrical 

 hollow spines. Height, 4 ; length, 9'5. 



Common ; found also in Australia. 







ORDER PECTINACEA. 

 Lobes of the mantle free through their whole length. 



FAMILY ARCID^;. 



Hinge of numerous teeth disposed in a straight or curved line ; 

 equivalve. 



BARBATIA. 



Oblong or sub-quadrangular, covered with a rough but perishable 

 epidermis ; hinge of numerous teeth, of which the central ones are the 

 smallest ; the lateral ones increasing in size and getting more oblique. 



107. B. Sinuata, LamarJc, I.e., vi., p. 462. Oval-elongate, mar- 

 gin sinuated, smooth or sometimes crenulated in the young, covered 

 with a brown hairy epidermis ; surface with fine radiating ribs, decus- 

 sated by longitudinal striae. Brown or yellowish ; interior white 

 varied with brownish purple. Height, T25 ; length, 2 '5. 



Common. Stewart's Island. Australia. 



. 108. B. pUSilla, Sowerby, Proc. Zool. Soc., 1833, p. 18. Ovato 

 sub-rhotnboidal, white, concentrically ridged and decussated at both 

 ends by radiating stria?, these striae being absent from a small portion 

 of the anterior central area ; anterior end short, rounded ; posterior 



