364 ESCHARID.E. 



RANGE OP VARIATION. Like its congener M. Peachli, this 

 species varies much in appearance under different condi- 

 tions of age and habitat ; but the characters are very con- 

 stant. When old, the cells are of a dead white colour ; 

 but in younger states they are bright and glossy. The 

 texture is delicate and somewhat vitreous at first, but be- 

 comes coarser and more granulous with age. Except in 

 the earliest states, the cells are almost always more or less 

 granular. The shape is generally ovate, sometimes rhom- 

 boid. The oral extremity is more or less elevated, and the 

 aboral immersed ; but this is often by no means a marked 

 character. The number of the spines is very constant ; 

 but occasionally a fifth is interposed between the pairs 

 which occupy the two sides of the aperture. The mucro, 

 which is always a striking feature, is at times exceedingly 

 broad and massive, and occasionally bifid. The ooecium 

 is sometimes subimmersed ; more commonly it is very pro- 

 minent ; but it is always closely united to the cell above it. 

 Not unfrequently all the spines project in front of the ovi- 

 cell ; but usually only one on each side is visible. 



HABITAT. On stones, shells, &c., from shallow to deep 

 water. 



LOCALITIES. Less common perhaps than M. Peachii, 

 but widely distributed. Shetland, 15-170 fathoms ; 

 Hebrides (A. M. N.) : Beaufort Dyke, 110-147 fathoms 

 (Capt. Beechey) : Sana Island (Hyndman) : Northum- 

 berland and Durham, deep water, rare (Alder) : St. 

 Andrews, deep water, not uncommon (Dr. M'Intosh) : 

 Belfast Bay (W. T.) : Dublin Bay ; Burnham, Norfolk 

 (Hassall) : Start Point (Bowerbank) : Cornwall, deep 

 water; Guernsey (T. H.) : &c. 



GEOGRAPHICAL DISTRIBUTION. France, S.W., 30-50 

 fathoms (Fischer) : Mediterranean (Manzoni) : New Zea- 

 land (F. W. Hutton) : Greenland, " the most abundant 



