General History of the Marine Polyzoa. 291 



guard the cells on each side, are the stable and distinctive 

 characters. There is much variability in the superficial 

 aspect, dependent on the amount of calcification, and different 

 portions of the same colony exhibit a striking diversity of 

 appearance. There is a great tendency to the formation of 

 nodules and papillary processes over the surface, and in some 

 states the numerous perforations are a feature. 



In the corner of the orifice below, a little behind the sinus, 

 are two rather large and prominent calcareous processes on 

 which the opercular hinge works. 



ScMzoporella inconspicua, sp. n. (PL VII. fig. 3.) 



Zoarium incrusting. Zocecia ovate, quincuncial, perforated 

 round the margin, gibbous, the front wall sloping up from the 

 margin to the centre, on the highest point, immediately below 

 the orifice, an umbo bearing a small avicularium^ with rounded 

 mandible, replaced in many of the cells by a broad spatulate 

 avicularium with a large median aperture, the lower margin 

 of which has a notch in the centre, whilst a prominent den- 

 ticle projects from the middle of the upper margin ; surface 

 nodulated and thickly punctured, sometimes areolated ; orifice 

 orbicular or suborbicular ^^ with a wide, shallow, rounded or 

 bluntly pointed sinus below, the articular denticles placed 

 one on each side at the entrance of the sinus ; the cell-wall 

 elevated round the orifice. Ocecium large, covering nearly 

 half the cell above it, of considerable width, much broader 

 than high, rounded above, the front surface flattened, shining, 

 thickly covered with minute perforations, surrounded by a 

 smooth border ; oral arch low and wide. 



Loc. Port Elizabeth, South Africa {Miss Jelly). 



As calcification proceeds the gibbous character of the zooecia 

 disappears ; but it is very apparent in the normal cells 

 towards the margin of the colony. In the central region the 

 orifice is deeply sunk, the walls thicken, the ooecia are sub- 

 immersed, and much of the characteristic aspect of the species 

 is lost. The structure of the avicularia offers some pecu- 

 liarities which may be available as diagnostic characters. 

 The orifice loith the sinus is pyriforra, but the portion above 

 the sinus, which is covered by the movable lid or true oper- 

 culum, is more or less orbicular. The hinge is placed at the 

 bottom of it between the articular processes^ which cause a 

 slight constriction and mark the commencement of the sinus. 

 It forms a well-marked boundary-line between the true oper- 

 culum and the extension of it which closes in the sinus. 



* lliUher ruduly orbiculiir, witli many slij.'-ht variations. 



