158 



results of former arrests of growth. At this stage of growth, too, the 

 radiating lines become obsolete. 



Pullial line entire, parallel with the base. Ligament external, lodged 

 in a rather deep groove. Hinge teeth obsolete or nearly so. Hinge 

 plate of the right valve swollen slightly and longitudinally under the 

 beaks, the swelling being bounded posteriorly by a short, obliixue exca- 

 vation. Posterior end of the hinge plate of the left valve maa-ked by a 

 narrow, oblique groove, ininiediately under the fulcrum and parallel 

 with it, evidently for the reception of the acute fulcral edge of the 

 right valve. 



Length of the largest specimen, twenty lines; height of the same, 

 twenty-one lines. In another individual the length is eighteen lines, 

 and the thickness through the valves is Just equal to the length, the 

 height being twenty lines. 



Nanaimo River, V. I., two miles and a-quarter up, in Division A. 

 A single cast. Sucia Islands, in the same Division, fourteen large and 

 nearly perfect shells, most of them with both valves; J. Eichardson, 

 18*72 and 1875. 



The S|,ecinien8 described above evidentl}' belong m Mr. Gabb's genus 

 Clisocolus, and are identical with the C. dubius of that author. Stoliczka 

 thinks that Clisocolus may be synonymous with Lori/pes of Poll, but the 

 former name may be conveniently retained for a group of fossil Lucinoid 

 shells, some of wliich have been described as Isocardice, which are 

 characterized not onl}- by their edentulous hinge, but also by their 

 globosely cordate shape and semispiral, divergent beaks. Isocardia 

 cretacea of Goldfuss is ))robably a Clisocolus, and appears to difter from 

 C. dubius only in its slightl}* more elongated form. 



The description of '' Sp/ueriola (?) cordata " (which Mr. Meek says 

 " may possibly belong to an undescribed genus ") applies so perfectly to 

 the Sucia Island examples of the present species as to leave very little 

 doubt in the writer's mind that C. dubius and S. cordata are different 

 names for the same shell. Spheriola endotrachys of Meek appears to be 

 an elongated variety of S. cordata, the roughnesses on the cast of the 

 former being probably due to a diseased condition of the mantle of the 

 animal. 



Opis Vancouverensis. (N. Sp.) 

 • Plate 18, figures 4 and \a. 



Shell inequilateral, subpyriform or ovately subtrigonal, about twice as 

 high as long, and widest near the base ; test thick. Anterior side very 



