ABT. 22. CYCLOSTOMATOUS BRYOZOA CANU AND BASSLER. 53 



D'Orbigny are the oldest; as all the genera of the Cytisidae are 

 comprised in the family as here adopted we employ this name. 



The study of this family shows that the mode of gemmation itself 

 is not a family character as in the Cheilostomata. 



The form of the apertiira is a good generic character; it is cer- 

 tainly in rapport with the disposition of the tentacles and of the 

 retractor muscles of the polypide. But the oblique and elongated 

 form of Cytis and its allies is found again in other families and 

 can not in any case be considered as an exclusive character. 



DICHOTOMODS KEY SHOWING STRUCTURE OF UENBRA. 



f Gemmation triparietal Cyrtopwa. 



] Gemmation biparietal 2. 



„ [ Tubes with peristome 3. 



I Tubes without peristomes 5. 



„ f Tubes expanded, grouped in linear fascicles Discocytis. 



I Tubes cylindrical 4. 



(Tubes grouped in linear fascicles on anterior face of zoarium. -Osculipora. 

 Tubes in orbicular zones around zoarium ; nematopores Plethopora. 

 No adventitious pores Plethoporella 



j Tubes exiiauded, neither mesopores nor nematopores Homoeosolen. 



' \ Tubes cylindrical 6. 



I Large ovicell, zoarium discoid Discocytis. 



\ Small ovicell, zoarium arborescent 7. 



^ f Vacuoles all around zoarium Desmepora. 



\ Nematopores dorsal 8. 



f Mesopores frontal Semicytis. 



' 1 No frontal mesopores 0. 



I One row of pinnules Vnicytiis. 



' \ Two rows of pinnules; one face smooth TruncatuUi . 



KEY FOB DETDBMINATION OF GBNBRA. 



1_ J Aperture orbicular 2. 



\ Aperture elongated, without peristome 5. 



2. j Tubes in linear fascicles 3. 



I Tubes grouped in orbicular zones 4. 



{Tubes increasing from the dorsal to the frontal in transverse 

 section (expanded tubes) Diplodesmopora. 

 Tubes of the same size in the transverse section (cylindri- 

 cal tubes) Osciilipora. 



4_ I No adventitious pores Plethoporella. 



\ Nematopores Plethopora. 



5. f Zoarium discoid Discocytis. 



\ Zoarium arborescent 6. 



6_ f One face smooth 7. 



1 No face smooth 8. 



[ Convex face smooth, no nematopores Homoeosoleri'. 



' { Concave face smooth, dorsal nematopores. Apertures at the 



l extremity of the pinnules Truncatula. 



^- I One row of pinnules Vnicytis. 



I Two rows of pinnules 9. 



I Tubes on the trunlc and on the pinnules. Frontal mesopores Semicytis. 

 Tubes at the extremity of the pinnules; vacuoles all around 

 zoarium Desmeporv. 



