Naviculacea.} infusorial animalcules. 505 



Appended sub-section LiTnoTTTECiA. 



This term was contrived by Ehrenberg, when he described 

 the genus Mesocena. The beings constituting this sub-section of 

 Naviculacea are far removed by general characters from the rest of 

 the family, and seem to form a transition group between Naviculacen 

 and Phytolitharia, which are illustrated by the siliceous skeletons of 

 sponges. 



Genus Actiniscus. — Individuals solid, with rays ; their figure 

 recalling that of a star. 



It differs from Bictyocha and Mesocena, in having a solid centre 

 or body, from which rays, varjnug in number and form, proceed. 



Actiniscus, together with Mesocena and Bictyocha, form the family 

 Actiniscece of Kiitzing ; who observes, that these beings were first 

 made known by Ehrenberg, in 1838 and 1840; and that, by their 

 peculiar form, they have little or no resemblance to other Biatomece. 

 They are all marine ; abundant in a fossil state ; and their shells have 

 numerous foramina piercing them. 



A. Stella. — Characters unknown. 



A. Biscus. — Disciform; centre smooth; eight marginal rays, not 

 exserted. Diameter 1 -2304th. Oran, in Africa. 



A. quinarius. — Stellate, with five exserted rays. Diameter 

 1-3 120th. ^gina. 



A. Hota. — Discoid; centre smooth, with ten exserted (projecting) 

 rays from its margin. Diameter 1-1 920th. Oran. 



A. Tetrasterias. — Stellate, with four exserted rays. Diameter 

 1- 1008th. Richmond, Virginia. This may belong perhaps to 

 PhytoUtharia. 



A. (?) Lancearius. — Stellate, with eight free (exserted) lanceolate 

 rays standing out from the margin, and some central shorter ones on 

 one side. Diameter 1 -240th. 



A. Pentasterias. — Stellate, with five siliceous rays ; centre solid, 

 concave. Diameter 1-1 150th. Alive in Norway, and fossil in 

 Greek marl. 



A. Sirius. — Stellate, with six acute rays expanded (alate) at the 

 base, centre solid. Diameter 1-1 150th. Alive, Christiana, Norway. 



Genus Dicttocha. — Individuals reticulate, spinous, free, solitary. 

 (Kiitz.) Characters by Ehrenberg, unknown. Marine. 



