Poh/zoa of Mauritius. 81 



Bmittia reticulata, J. MacG. 



Tlie zooecia of the Manritiiis specimen are smaller than those 

 of the British form ; the lateral denticles are riiclimentarj and 

 have disappeared in some cells. The avicularium points 

 obliquely instead of vertically downwards, as in the British 

 form. 



Genus Poeella. 



Porella nitidissima^ Hincks. 



Porelln nitidisshna, Hincks, Ann. & Mag. Nat. Hist., July 1880. 

 The only specimen hitherto found comes from Madeira. 



Genus Muceonella. 

 MucronelJa porelliformiSj n. sp. (PI. IX. fig. 1.) 



Zoarium incrusting. Zooecia small, rhoraboidal, surface 

 glistening, verrucose ; orifice suborbicular, lower margin not 

 dentate ; peristome raised in front into a broad, convex, 

 hammer-shaped process, finely crenate at the top ; in young 

 cells a small process rising from the peristome on each side of 

 the orifice and bending inwards ; six oral spines ; on each 

 side of the orifice a slender avicularium, with acute triangular 

 mandible pointing upwards and outwards. Ooecia small, 

 recumbent, vitreous, not punctured. 



The species is called " porelUformis " from the appearance 

 presented by the orifice. The large pouch-like macro arches 

 over the orifice in such a way as to give the cell the appear- 

 ance of possessing a secondary orifice resembling that of 

 'Porella. This is especially the case when one or both of the 

 lateral processes blend with the median. There is no avicu- 

 larium on the inner side of the pouch thus formed. 



Mucronella cothurnica^ n. sp. (PI. IX. fig. 5.) 



Zoarium incrusting, zooecia forming linear series ; walls 

 thick, coarsely punctate. Zooecia large, oval below, rising to 

 a tall peristome surmounted by about twenty stout jointed 

 spines nearly encircling the orifice, except a small space in 

 front ; orifice subquadrangular ; anteriorly a grooved, trian- 

 gular, horizontal mucro. Avicularia none. Ooecia small, 

 globular, punctured. 



