444 Rev. T. Hineks on the 



slightly elongated, and projects a little beyond the anterior 

 extremity of the beak. In the present variety this elongation 

 has been carried very much further, and at the same time a 

 narrow chitinous expansion seems to have been developed 

 along each edge of the setiform process thus formed. In this 

 way a tall vibraculoid organ has taken the place of the normal 

 mandible. The beak survives ; but it too has undergone a 

 certain amount of modification, tending to secure freer play for 

 the movable seta. In general character the present variety 

 agrees entirely with the ordinary forms of AL ciliata. 



A glance at the three varieties represented on PL XVII. 

 (figs. 1, 2, 3) will suffice to show what an amount of super- 

 ficial difference there may be within the limits of one and the 

 same species, and may well suggest those structural elements 

 which should have most significance with the systematise as 

 indications of genetic affinity. 



MtcroporeUa ciliata, form umbonata t n. (PI. XVII. fig. 1.) 



An umbonate process placed on each side of the orifice. 

 Below the inferior margin a massive mamillary rising, 

 which, when fully developed, conceals the pore. The entire 

 surface thickly covered with rather large punctures, which are 

 sometimes arranged in radiating lines. 



& V,w ^ *<..v*»„.i*x*£, 



Loc. Dolomite Narrows, on stone. 



lifornica. (PI. XVII. fig. 3.) 



epralia calif < 

 pi. xi. fig. 6. 



This variety is abundant amongst the dredgings. The 

 roecium is sometimes very prettily adorned with ribs radiating 

 from a central boss towards the base. 



Microporella Malnsii ) Audouin. 

 Extremely abundant and very fine ; one of the commonest 



Bpecies. 



MoNorouELLA, Ilincks. 



Monoporella brtmnea, n. sp. (PI. XVIII. fig. 4.) 



Zcacia ovate or sometimes lozenge-shaped, quincuncial, 

 moderately convex, separated by fine lines, sutures well de- 

 fined ; surface glistening, minutely granulated, punctured and 

 reticulate, the punctures often more or less obliterated by 

 the calcification ; orifice arched above, lower margin straight 

 or slightly curved inward, peristome not raised ; the cell-wall 





