117 



L. FENESTRALIS. Eucrusting, calcareous; cells ur- 

 ceolate, slightly immersed, semi-erect, and reticulated ; 

 aperture contracted, circular, with a slight tooth on tha 

 proximal lip. PI. xxii., fig. 0. 



Hab. On stones at short distances from the shore, not 

 uncommon. 



This rarely exceeds three fourths of an inch in diameter; 

 it is calcareous and encrusting. The cells are urceolate and 

 closely arranged in circular rows; they do not, like most 

 other species, lie horizontal to the crust, but the oral por- 

 tions are elevated, or semi-erect. The surface of the cells 

 is rough; several calcareous lines run longitudinally their 

 whole length, and these are crossed nearly at right angles 

 by shorter bands, which give the surface a network appearance 

 with square meshes. This window-like surface, has tho 

 interspaces filled with a transparent membrane, which is 

 more apparent in dried, than in living specimens. Tha 

 aperture is small, contracted, and circular, with an irre- 

 gularity on the proximal lip. 



L. RETICULATA. Encrusting, calcareous; cells urceo- 

 late, reticulated ; apertures semi-circular. PI. xxii., fig. 9. 



Hab. On stones &c, not uncommon. Polperro, Lan- 

 sallos bay; Goran, Mr. Peach. 



This species encrusts the surfaces of stones, about low- 

 water mark, in patches varying to an inch and halt' in di- 

 ameter. The cells are urceolate and nearly horizontal and, 

 though not heaped together, have no constant order of ar- 

 rangement. The cells are rough. From the aperture down 

 the centre of the cell lines diverge obliquely downwards and 

 outwards to the sides of the cells ; these are again crossed 

 by lines in an irregular manner; hence the surface has a 

 reticulated appearance. The interspaces or depressions 

 formed by these lines are translucent. The lines, however, 

 are not alike in all the cells; but there is always an approach 

 to the above description, which m iy therefore be taken as 

 a type of the whole. The apertures are semi-circular or 

 halt-moon shaped, large, with a raised rim, which is most 

 apparent in dried specimens. 



This differs from L. feneslralis in several particulars; the 

 cells are larger and more horizontal; the reticulations of no 

 regular form, being sometimes square and at others rhom- 

 boidal. The lines forming the reticulations diverge from a 

 median line, instead of running longitudinally as in L. fenes~ 

 trails ; in this the aperture is large and semi-circular, in the 

 other contracted and round. 



P 



