293 



instructus ; dentibus lateralibus remotis, validis. Long. ^ ; alt. f ; 

 lat. I poll. Hah. Oregon. 



This is to be compared with C. cornea on account of the 

 peculiar rounded form of the dorsal region, the umbones not 

 rising so as to interfere with the general outline. The cavity of 

 the beaks is still more shallow, the sulcation coarser, and the 

 color yellowish rather than green, and on the whole the shell is 

 more dense and larger. 



Cyrena debilis. T. parva, tenuis, transverse ovata, postice 

 ampliata et subtruncata, sub-equilateralis, concentrice liris con- 

 fertis, sub-reflexis arata, epidermide nitido, superne olivaceo 

 induta ; umbonibus parum elevatis, erosis, absque lunula : intus 

 violaceo-albida ; dentibus cardinalibus inconspicuis, dentibus 

 lateralibus elongatis, striatis. Long, j^q ; alt. j^; lat. ^ poll. 

 Hah. New Holland ? 



Most like C. pusilla, but has no areola in front of the beaks, is 

 less orbicular, and somewhat larger. In general it resembles a 

 Cyclas. 



Anodon glauca. T. transversa, elongato-ovata, ventricosa, 

 antice rotundata, postice oblique rotundato et costa obliqua sub- 

 marginali munita ; margine dorsali arcuato; margine ventrali 

 concave ; umbonibus antemedianis, acutis, parum elevatis ; epi- 

 dermide olivaceo-glaucescente fluctuatim corrugato induta : ca- 

 vositas argentea ; disco salmonaceo : cardo edentulus vel potius 

 papilla cardinal! in valva dextra instructus. Long. If ; alt. |- ; 

 lat. ^ poll. Hah. Peru. 



The peculiar dead rusty-green color of the epidermis, with its 

 loop-like corrugations may serve as distinctive marks. It would 

 come under the genus Monocondylea of D'Orbigny. 



Anodon feminalis. T. solidula, transversa, ovato-triangu- 

 laris, antice acuminata, margine postico in margine dorsali con- 

 tinue, arcuato ; margine ventrali recto ; apice rectangulari ; 

 umbonibus inconspicuis, erosis, anticis, declivitate posticali 

 obtuse angulato ; epidermide lamelloso, piceo : margarita pur- 

 purascens ; limbo argenteo ; dente cardinali obsolete. Long. 

 2J-; alt. L] ; lat. J poll. Hah. Oregon. 



At first this was supposed to be the young of A. angulaia^ 

 Lea ; but it proves different in several constant characters, be- 



