220 



Synopsis of the genera. 



1) The inner surface of the frontal wall with a rounded cryptocyst 

 lamina (issuing from the proximal margin of the primary aperture), 

 the free margin of which is most often distinctly visible through the 

 frontal surface, especially through its fenestrse: 



2) The hinge-teeth slightly developed and indistinct: 



3) The frontal surface with numerous, scattei'ed pores; the inner 

 calcareous lamina short and broad and only seen distinctly from the 



inner surface of the frontal wall Cribricella n. g. 



3) The frontal surface with from three to twenty odd (more rarely 

 onh' a single) larger or smaller fenestras or pores disposed in a con- 

 tinuous curve or in an angle; sometimes within the area bounded by 

 the fenestrse transverse fissures more or less regularly arranged in pairs; 

 the free margin of the internal calcareous lamina generallj' clearly vis- 

 ible through the fenestrse. 



4) Within the area bounded by the fenestrse a larger or smaller 

 number of transverse fissures separating more or less developed, gener- 

 ally hollow spines. 



The lateral chambers wholly or almost wholly calcified; the ad- 

 zocecial, scapular chamber of the daughter-zooecium developed into an 

 avicularium Costicella n. g. 



4) No transverse fissures found within the fenestrse; at most 2^5 

 rudimentary spines on the proximal side of the aperture ; lateral cham- 

 bers mostly membranous: the scapular chamber on the adzooecial side of 



the daughter-zooecium not developed into an, avicularium Scuticella n. g. 



2) Strongly developed hinge-teeth in the shape of robust, conical 

 or cylindrical processes, generally freely projecting within the aperture: 



5) The zooecia with 2 — 4 cylindrical, acropetal spines distally, and 

 a rudimentary circular pedal chamber proximally; the aperture with a 



deep, rounded sinus Claviporella Mac Gillivray. 



5) No cylindrical acropetal spines: 



6) The aperture, not surrounded by a protruding margin; the four 

 lateral chambers forming on each side a continuous, wing-like mar- 

 ginal portion in the whole length of the zooecium; the adzooecial side 



of the mother-zooecium with an avicularium Pterocella n. g, 



6) The aperture surrounded by an acutely protruding sometimes 

 bilobate margin; the lateral chambers forming no wing-like marginal 



