Naviculacea.^ iNFTJSoniAL animalcttles. 315 



AcTiNOPTYcmjs dives. — Found fossil at ^gina, with last species. 



A. Ceres. — Has twenty-two rays. Diameter 1 -336th.' Virginia. 



A. qxiatmrdeiiarius, fourteen septa and rays. Mouth of the Elbe 

 and America. 



A. octonarius, eight partitions ; same habitation ; and in polishing 

 powder of Or an. 



A. sedcnarius, sixteen septa. Diameter 1 -288th. Cuxhaven and 

 Richmond, Virginia. 



A. octodenariifs, eighteen septa. Diameter 1 -240th, Cuxhaven. 



A. dmdcnarim, twelve rays and septa. Cuxhaven. 



Genus Amphipentas. — Unattached; lorica simple, bivalve, and 

 pentagonal. 



This genus is not yet well established, it being open to question 

 whether its supposed species may not be fragments of other 

 organisms. 



A. alternans. — Pentagonal ; sides concave ; angles obtuse ; the 

 angles of the external pentagon alternating with those of a smaller 

 central one; the latter has also a cii'cular projection at its middle. 

 Cuba. (P. 14, f. 32.) 



Is it a calcareous particle of an Echinoderm ? If Coniopelta ? 



A. Pentacrimis. — Pentagonal ; its dorsal surface presenting a 

 striated ring. Diameter 1 -240th. Fossil in Greek marl. Fragments 

 like Am/pTiitetras. 



Genus AMPmrLEURA, (Kiitz.) — Frustules solitary, navicular, 

 prismatic, longitudinally furrowed ; without central aperture. 



This is one of the genera included in the family ITaviculea by 

 Kiitziug, but one not well defined. 



A. pellmida. = Navicida? pellucida, (Ehr.) — Slender, elongated, 

 liaear lanceolate, not transversely striated, apices obtuse. (P. 16, f. 1.) 

 Length 1-2 76th. to 1 -204th. German Coast and Falaise. 



A. Lanica. — Short, lanceolate, truncate, not striated. (1 -390th.) 

 Danish Coast. 



A. rigida. — Elongate, linear lanceolate, truncate ; on one aspect 

 straight; on the other sigmoid. (l-168th. to l-144th.) Marine. 

 (P. 16, f. 2.) 

 y 2 



