CHOKIZOPOKA BllONGNIARTII. 225 



cells are usually elongate and pointed below ; but a shorter 

 form occurs, which is rounded off at the base. The tex- 

 ture of the cell-wall is generally very delicate and trans- 

 lucent, and the surface smooth and shining. In one 

 variety, however, the cells are strongly furrowed trans- 

 versely; they are also frequently traversed by delicate 

 longitudinal striae. The mucro (which is sometimes 

 wanting altogether) is often placed immediately below 

 the inferior margin, rising above it, and projecting over 

 the mouth. When thus placed it is expanded at the 

 base, and tapers off to a sharp point above. It also 

 occurs lower down on the cell-wall, and is not unfre- 

 quently central. The keel on the front of the ovicell is 

 often wanting. 



HABITAT. On shells, stones, Fucus, &c., from shallow 

 to deep water. 



LOCALITIES. South Devon, very abundant ; Ilfracombe, 

 on Laminaria; off the Deadman, 60 fathoms; Isle of 

 Man (T. H.) : Tenby (F. Walker) : Hastings (Miss Jelly): 

 Northumberland, rare; on a stone from deep water, 

 Cullercoats (Alder) : St. Andrews, on Laminaria-roots 

 thrown ashore after storms, rather plentiful (Dr. 

 M'Intosh) : Ayrshire (Landsborough) : off Sana Island 

 (Hyndman) : Shetland, 40-100 fathoms, frequent 

 (A. M. N.) : Dublin Bay (Hassall) : Birterbuy Bay 

 (G. S. Brady) : &c. 



GEOGRAPHICAL DISTRIBUTION. Mediterranean (Busk) : 

 Algiers (J. Y. J.) : Adriatic, on shells, not rare (Heller) : 

 on the Falmouth-Lisbon cable, between N. lat. 47 58' and 

 47 35' and in W. long. 7 6', from 89-205 fathoms (Sir 

 J. Anderson) : Roscoff (Joliet) : France, S.W. (Fischer). 



RANGE IN TIME. Coralline Cra (Searles Wood) : 

 Pliocene deposits at Voltcrra and Castrocaro (Manzoni) : 

 Austro- Hungarian Miocene (Keuss). 



Q 



