MICROPORELLA IMPRESSA. 215 



Range of Variation, The cells vary slightly in form, 

 being sometimes rather irregularly ovate, and at others of 

 a very neat and definite diamond- or lozenge-shape. The 

 punctures are diffused over the surface, or merely ranged 

 in a single line round the edge of the cell. The umbo is 

 occasionally wanting, and at times is of great size and 

 fantastic form. The ooecium is either simply globose and 

 punctured, or keeled down the front and umbonate. 



Habitat. On weed, stones, and shells, from tide-marks 

 to deep water (30—10 fathoms). Chiefly a littoral form. 



Localities. South Devon ; Ilfracombe, under ledges 

 on the Capstone ; off the Deadman, Cornwall ; Isle of Man 

 (T. H.) : Bamborough, tide-marks (Alder) : Holy Island 

 and Berwick (Johnston) : St. Andrews, near low-water 

 mark (Dr. M'^Intosh) : Ayrshire (Landsborough) : Shet- 

 land, tide-marks (Norman) : island of Stroma (C. W. P.) : 

 Ireland (Mrs. Gatty). Var. coi'nuta : — Lambay Island 

 (W. T.) : Salcombe Bay; Guernsey, on red weed (T. H.). 



Geographical Distribution. Algiers (J. Y. J.) : France, 

 S.W. (Fischer) : RoscoflP (Joliet) : Bergen (A. M. N.). 

 Var. a. Naples (Waters) . 



There can be no doubt of the identity of L. granifera, 

 Johnston, with the Flustra impi'essa* of Audouin; and 

 the more familiar name must give place to the earlier. 

 The figure in Savigny's work represents our var. /3 (glabra) 

 with great fidelity. 



The Crag form, Lepralia pyi'iformis, Busk, agrees 

 exactly with the present in every point but the absence of 

 the median pore ; it ought, I think, to rank as a variety. 

 The diffusion of the punctures over the entire surface of 

 the cell is not, as j\Ir. Busk supposes, uncommon in our 

 M. impressa. 



This is a very brilliant species — in its young and fresh 



* The EscJiara iinpvcssa of Mull is a StcganoporcUa. 



