186 



Species. 



1. anoraala, Mull. 3. radiosa, Gould. 5. rostrata, id. 



2. personata, Lam. 4. ringens, Honing. 



Figures. 



Crania anomala. PI. P. Fig. 9. Shell, in its natural position, attached 

 to stone. Fig. 8, and PL 26. Fig. 152. Shell, showing the muscle- 

 scars and nose-like projection on the inner surface of the adherent 

 valve. 



Genus 4. ORBICULA, Lamarck. 



Animal ; with two rather short cirrhated arms, unprovided with 

 any apophysary skeleton, folded within the concavity of the upper 

 valve ; foot with an adherent tendinous pedicle passing through 

 a slit in the lower valve. 



Shell ; inequivalve, orbicular, horny ; upper valve convex, limpet- 

 like, lower valve fissured for the passage of a tendinous pedicle, 

 and furnished internally toith a process for the support, at their 

 origins, of the cirrhated arms. 



Like the Crania the Orbiculce are closely adherent mollusks, and the 

 ventral valve is the undermost ; the shell is, however, of a less calcareous 

 substance, horny and flexible, and does not become agglutinated to the 

 place of attachment. Adhesion to foreign bodies is acquired by means of 

 a tendinous pedicle, not passing out of a beaked projection of the upper 

 valve, as in Terebratula, but through a fissure in the valve upon which the 

 animal rests. The brachial appendage, which has no supporting apophy- 

 sary skeleton, is folded within the concavity of the upper valve. 



One species, 0. lavis, is Scandinavian, the rest are chiefly from the 

 shores of Chili and Peru. 



Species. 



1. Cumingii, Brod. 4. lamellosa, Brod. 6. strigata, Brod. 



2. Evansii, Dav. 5. striata, Sow. 7. tenuis, Soto. 



3. lasvis, Sow. 



