Mr. T. Whitelegge oyi Australian Polyzoa. 15 



character which, if not new to the class, is exceedingly rare, 

 and so far I have searched in vain for the record of a similar 

 structural element. 



The first indication of the formation of a new zooecium 

 appears on the upper surface of the zoarium as an elevated or 

 depressed round spot bordered on one side by a thin layer of 

 epitheca. At this point the " semilunar slit with the con- 

 cavity directed outwards " is formed, and by the gradual 

 extension of this slit to a circular form a piece of the calca- 

 reous lamina is cut out, the resulting opening being that of 

 the peristome, and at a short distance below the true oral 

 aperture is seen to be also in a fully formed condition. It is 

 the rule to speak of the operculum-bearing aperture as the 

 primary and of the peristomial as the secondary orifice ; but 

 in this case it appears doubtful which ought to rank as primary 

 or secondary. 



In a median line above the mouth, close to or upon the 

 margin of the peristome, there is a circular or subcircular pore 

 usually covered by a membrane. It is this pore, when in an 

 imperfect or broken state, that has been mistaken for the 

 proximal sinus in the lower lip of the oral aperture ; but the 

 true oral sinus is much wider and at the opposite end of the 

 mouth to that of the pore. 



The shape of the oral aperture generally approaches that of 

 Cellepora eatonensis as figured by Busk in the ' Ciiallenger ' 

 Polyzoa, pi. xxix. fig. 5 b ; but the sinus varies in width so 

 much that in some cases the aperture might be described as 

 oval, with two lateral denticles at the base. 



It is evident that the seven species already enumerated are 

 closely allied to each other and can no longer remain in the 

 various genera to which they have been referred. They do 

 not belong either to the genus LunuUtes or to Cupularia, 

 and the genus ConeschareUina^ as at present defined, would 

 not admit them ; the same may also be said of Flahellopora. 

 Mr. A. W. Waters, in referring to LunuUtes incisa, H., says 

 it " is a species of the Schizoporellidse." Nevertheless, to 

 whatever family they may ultimately prove to be related, at 

 present I venture to make a new genus for their reception, 



BiPORA, n. g. 



Zoarium uni- or bilaminate, conical, or forming lobate or 

 flabellate expansions ; growth intercalary ; zooecia immersed, 

 erect, side by side, with their bases resting on a cancellated 

 lamina, forming alternating rov/s directed to the primary part 

 of the zoarium ; oral aperture with a well-marked sinus in 



