MEMBRANIPORA TRIFOLIUM. 167 



shell; Guernsey (T. H.) : Antrim (Hyndman) : Peter- 

 head and Wick (C. W. P.). 



GEOGRAPHICAL DISTRIBUTION. Algiers (J. Y. J.) : Bay 

 of Gibraltar (M'Andrew and Landsborough) : Adriatic, on 

 Tellina depressa (Heller). 



MEMBRAXIPORA TRIFOLIUM, S. Wood. 

 Plate XXII. figs. 5, 6. 



FLUSTRA TRIFOLIUM, Searles Wood, Ann. N. H. sen. 1, xiii. 20. 

 MEMBRANIPORA TRIPOLIUM, Busk, Crag Pol. 32, pi. iii. figs. 1, 2, 3, and 9 



(part.). 



MEMBRAMPORA SOLI DA, Packard, Labrador Anim. (1860), 8, fig. 2. 

 MEMBRAMPORA SACCDLATA, Norman, Ann. N. H. ser. 3, xiii. (1864), 88 



(8 sep.), pi. xi. fig. 3. 

 MEMBRAMPORA FLEMINGII, forma TRIFOLIUM, Smitt, CEfv. K. Vetensk.- 



Akad. Forh. 1867, no. 5; Krit. Forteckn. pt. iii. 367 and 



405, pi. xx. fig. 42. 



Zocecia lozenge-shaped, or ovate, or elongate, arched and 

 wide above and narrowed downwards; the lower part 

 of the area covered in by a thin, minutely granular 

 lamina; aperture ample, trifoliate; margin elevated, 

 crenated. Avicularia sparingly developed, raised, 

 placed between the cells ; mandible acute, directed up- 

 wards or downwards. Ooecia semielliptical, smooth, 

 but having on the front a triangular space, bordered 

 by a raised line, which is minutely granular. 



Colonies of a pale olivaceous-green colour. 



Var. a (quadrata}. Margin of the cells very prominent 

 and strongly crenated, rarely two spines at the top, one 

 on each side. Occasionally a prominent avicularivm 

 on the lamina, near the bottom of the cell, placed 

 obliquely ; mandible pointing downwards and outwards. 

 Ooecia globose, bordered in front by a raised line, 

 inclosing a somewhat qxiadrangular space, which is 

 minutely granulated. 



Colonies forming subchrular, mldih-bro\vn crusts. 



