8CRUPOCELLA11IA SCRUl'EA. 51 



short, ovate above, produced and slightly narrowed 

 below ; aperture oval, occupying about half the front, 

 with three spines on the outer margin above, and one, 

 or occasionally two, on the inner. Operculum somewhat 

 reuiform, entire, narrow and pointed above, expanded 

 below and rounded, the upper extremity elevated. 

 Lateral avicularia large and conspicuous, with a strongly 

 hooked beak; small raised avicularia sometimes dis- 

 tributed along the median line, often wanting. Vibra- 

 cular cell erect, somewhat wedge-shaped. Ooecia 

 rounded; surface smooth, shining and imperforate. 

 Height i to | inch. 



HABITAT. On Algse, stones, &c. from shallow and deep 

 water. 



LOCALITIES. OS Dartmouth (E. Forbes) : Cornwall, 

 off St. Ives, on stones ; off Berry Head, Torbay ; Sal- 

 combe Bay, not uncommon ; Guernsey (T. H.) : North- 

 umberland, from the deep-water boats, a single specimen 

 (Alder) : the Minch (A. M. N.). 



GEOGRAPHICAL DISTRIBUTION. Mediterranean (M'An- 

 drew) : Adriatic (Grube and Heller) : Australia (MacGilli- 

 vray) : Singapore (Liverpool Free Museum, teste T. H.). 



This species has an operculum with a simple, un- 

 branched, and perfectly smooth lamina, and in this respect 

 differs both from S. reptans and S. scabra, the only other 

 British operculatcd forms. 



The avicularia, which are disposed along the front sur- 

 face of the zoarium, are very small; and I have only noticed 

 them where the ooccia are present; they are certainly 

 very sparingly developed. They are placed immediately 

 above the ovicells, with the mandible directed alternately 

 towards opposite sides, and probably rise from the front 

 or side of the cell a little below the aperture. 



K 2 



