SMITTIA RETICULATA. 347 



rences of appearance, dependent upon age, locality, &c. ; 

 but there is very little variability in important characters. 

 Sometimes the zocecia are margined by a row of circular 

 pores ; sometimes they are very prettily areolated round 

 the edge*. 



Commonly the avicularia are elevated, and project in 

 front of the lower lip ; but in one of the best-marked 

 varieties they are immersed and of smaller size than 

 usual, the cells are flat, punctured round the sides, and of 

 dense texture; the margin of the orifice is but slightly 

 raised ; and the oo3cium is closely united to the cell above, 

 and not so prominent as in the common form (Plate 

 XLVIII. fig. 2). 



A curious monstrosity has occurred to me, in which 

 two cells have but a single ovicell between them, which 

 is of great breadth, and overarches the two openings. 

 The cells are somewhat narrowed ; and the avicularia are 

 turned a little to one side (Plate XLVIII. fig. 3). 



HABITAT. On shells, stones, corals, &c., chiefly from 

 deep water. 



LOCALITIES. Guernsey ; South Devon ; Cornwall, espe- 

 cially on Pinna, from 40-60 fathoms (T. H.) f : Norfolk 

 (Lieut. Thomas) : Northumberland, on shells from deep 

 water, not rare (Alder) : Aberdeen (Macgillivray) : St. 

 Andrews, not uncommon in the siphons and inside the 

 mouth of Fustis antiquus, and on Cardium, from deep 

 water (Dr. M'Intosh) : Loch Fyne (Lady Emma Camp- 

 bell) : Wick and Peterhead (C. W. P.) : Shetland, rare, 

 80 fathoms (A. M. N.) : Belfast Bay, deep water (W. T.) : 



* This difference is probably dependent upon age. The youngest cells 

 are perfectly smooth, the walls extremely thin, and perforated round the 

 edge by a number of circular pores. 



t One of the most abundant species on the Cornish Pinna, from 60 

 fathoms, forming exquisite patches on the interior surface of the shell. 



