28 



It was found in exposed situations. — G. B. S. 



Chiton Frembleii. Chit, testa oblongd, complanatd, olivaceo* 

 fused, lineis albido-viridibus varid ; valvce anticce radiis elevatis 

 subgranosis ; intermediarum marginibus angulosis, areis lateralibus 

 biradiatis, radiis subgranosis, interstitiis longitudinaliter subsul- 

 catis; limbo setis brevibusfrequentibus obsito: long, l^lat. ] poll. 



Hab. in Sinu Valparaiso. 



This species differs from Chit, setiger, King, in being much flatter, 

 in the more angular margins of its intermediate valves, and in its 

 more numerous and much shorter bristles. 



It was found only on one exposed rock covered by a small species 

 ofFucus.— W. J. B. 



****** Ligamento marginis piloso. 



Chiton scabriculus. Chit, testa ovali, planiusculd, cinered, 

 albido-variegatd ; valvd anticd, areis lateralibus valvarum inter- 

 mediarum et parte posticd valvce posticce radiatim scabroso- 

 lineatis ; valvis intermediis et parte anticd valvce posticce longi- 

 tudinaliter sulcatis ; limbo piloso, cinereo, rufo-articulato : long. 

 If, lat. ^poll. 



Hab. ad littora America? Centralis. (Guacomayo and Puerto 

 Portrero.) 



Found under stones. — G. B. S. 



******* Ligamento marginis fasciculato-piloso. 



Chiton retusus. Chit, testa oblongd, postice relusd, pallescente ; 

 valva anticd, areis lateralibus valvarum intermediarum et valvce 

 posticce area posticd turgidis, radiato- sulcatis ; areis centralibus 

 valvarum intermediarum et area anticd valvce posticce sulcato- 

 asperis ; ligamento marginis fasciculis pilorum minimis plurimis : 

 long. liV, lat. -^y poll. 



Hab. ad oras America? Centralis. (Guacomayo and Puerto Por- 

 trero.)— G. B. S. 



Genus Placunanomia. 



Testa adhserens, subsequivalvis, irregularis, complanata, marginem 

 versus plicata, interne vitrea. Cardo internus, dentibus duobus 

 elongatis, crassis, subcurvis, divaricatis, basi convergentibus in 

 valva inferiore, sulcis duobus ligamentiferis in superiore. Valva 

 inferior cardinem versus superficialiter irregulariter externe fissu- 

 rata, organo adhaesionis subosseo inter testas laminas inserto et 

 externe fissuram implente. Impressio muscularis in utraque valva 

 subcentralis. In valva superiore organi adhaesionis impressio super- 

 addita. 



This interesting genus partakes of the characters of the genera 

 Ostrea, Plicatula, Placuna, and Anomia. It may be regarded as 

 the connecting link between the two latter. With an arrangement 

 of the hinge approaching very nearly to that of Placuna, it has the 

 distinguishing organization of Anomia, while the external appear- 

 ance of the shell, especially if viewed in situ, bears the strongest 

 resemblance to a Plicatula or some of the plicated Oysters, The 

 organ of adhesion, which in its bony character (for it is more bony 



