APPENDIX. 433 



yellow granulated mass within them. Diameter 1 -860th 

 to l-240th. 



773. COSCINODISCUS radiatus. Shell-like lorica large, 

 marked with moderately sized cells, disposed in lines, radiat- 

 ing from the centre ; towards the margin the cells become 

 smaller in size. Found in the fossil condition, very abun- 

 dantly, in the chalk marl of Oran, and alive, in sea water, 

 near Wismar and Cuxhaven. Diameter 1 -860th to 1 -240th. 



774. DICTYOCHA aculeata. Cells arranged by sixes, in 

 the form of a ring, each cell being spiny within. Spines six 

 in number, long, but unequal in length, and radiating 

 from the circumference. Found fossil in the chalk marl 

 of Oran, Caltanisetta, Zante, and Greece ; alive in the 

 waters of the Cattegat, near Tjorn. Diameter of the fossil 

 forms l-2304th to l-1150th; of the living, l-1440th to 

 1-1 150th, without reckoning the horns. 



775. DICTYOCHA fibula. Cells arranged in fours, 

 in a concave rhomboid, or square form, having connected 

 spiny angles. Found fossil in the chalk marl of Oran and 

 Caltanisetta, and alive in sea water near Christiana. Loco- 

 motion not observed. Diameter 1-1 150th to l-560th. 



776. DICTYOCHA pentasterias. Cells not present, centre 

 solid and concave" Five siliceous rays are present, forming 

 a sort of star. Found fossil in the chalk marl of Greece, 

 and alive in sea water at Christiana. This species is 

 devoid of colour, and locomotion was not seen. It resem- 

 bles Arcella. Diameter 1-1 150th. 



777. DICTYOCHA sirius. Cells not present, centre solid. 

 The six siliceous rays are broad or winged at the base, but 

 acute at the extremity. This species is not known in the 

 fossil condition, but is found alive in sea water near 

 Christiana. Diameter 1-1 150th. 



778. DICTYOCHA speculum. Cells arranged by sixes in 

 the form of a ring, spines six, long, but unequal in size, 

 radiating from the circumference, cells not spiny within. 

 Found fossil in the chalk marl of Caltanisetta, Oran, and 



2 F 



