BHITISH PALAEOGENE BRYOZOA. 243 



In regard to Adeonellopms, it seems to me absolutely necessary to accept that or Busk's 

 [No. 8, p. 178] Beptadeonella, as it is going rather far to place such a species as 

 '^Lepralia " violacea, Johnst., in Adeona or Microporella. Beptadeonella is prior by two 

 years, but it was based only on zoarial characters and was never properly diagnosed, 

 and I therefore prefer to accept Macgillivray's better defined genus [No. 2, pt. ix. 

 p. 134, and No. 3, p. 210]. 



Eeuss has described another species which it is necessary to consider in connection 

 with the Microporellidse, as it possesses both a trypa and an oral sinus. The species 

 which shows this feature is of such interest in connection with the evolution of this 

 group that it is advisable here to diagnose the new genus necessary for its reception. 



SCHISJIOPORELLA^ n. g. 



Diagnosis. Zoarium lepralian or escharine. 



Zooecia elongate, oblong (in known species). Aperture orbicular, with a large sinus. 

 The front wall has a zocecial pore. 



Ocecia external, globose. 



Type species. Sckismoporella schizogaster (Reuss)-, 1847, Helvetian, Austria. 



This genus may at first throw doubt upon the assumed homology of the sinus and 

 trypa, the latter being regarded as the more specialized. The occurrence of Schismo- 

 porella may, however, be explained by a repeated formation of a sinus after the zocecial 

 pore has travelled well away from the peristome : or else the division of the tiypa 

 into two or more pores has very frequently taken place, and there seems no impro- 

 bability in one of these parts persisting as a sinus. If neither of these explanations is 

 con'ect, then Schismoporella is probably a primitive form uniting characters now divided 

 between two families. 



The following synopsis summarizes the classification of this group that is here 

 proposed: — 



Schizo- 

 thyriata. 



'' Schizoporellidee : schizostomatous. External ooecia. 

 Adeonellida : primary aperture schizostomatous. Gonoecia. 



f Adeonintfi : with f Zoarium feuestrate, &c. Adeona. 



gonoecia. \ „ foliaceous or encrusting. Adeonellopsis. 



Microporellidce : 1 Micrajjorellinece : = Microporella, Tessarodoma, &c. 



trypa present. external marsupia. 



Schismoporellinte : = Schisinoporella. 



with trjrpa and sinus. 



' rrom (T^iafia, a slit, and iropos, a pore. 



' Cellepora schizoyasUr, Eeuss, 1847, No. i, p. 84, pi. x. fig. 9 ; Mollia schizogaster, D'Orbigny, >fo. 2, 

 p. 388 ; Lepralia schizogaster, Reuss, No. 14, p. 161, pi. iiL fig. 10. 



VOL. xin. — PAET Ti. No. 4. — JvMe, 1893. 2 n 



