286 
ELEID^. 
of the principle on which von Hagenow’s Salpingina liad been 
founded thirty years before ; for the ‘ Zellen ’ of the external layer 
in Meliceritites are only the expanded end of thp zooccia which 
form the central bundle. And in neither Hammia nor Cyrtopora 
(see Figs. 29 and 30) is there any such expanded distal end or 
external zone of cells round an axial bundle of tubes. 
Fig. 30 . — Cyrtopora degans, Hag. A longitudinal section, x 14 dia. 
Maastrichter Kreide. Maastricht. Van Breda Coll. D. 3326. 
Marsson, in 1888, dhided the Cyclostomata into two ‘ t}*pi,’ 
the 8olenoporina, including all except the Ceidte and Eleidoe, for 
which he founded the ‘ typiis ’ Metopoporina, which he defined as 
follows : — “ Zellrohren aus enger Basis nach vorn zu sehr erweitert, 
oft fast trompetenartig, mit einer rhombisch-sechseckigen Stirnwand 
an die Oberflache tretrend. ^Miindung klein, nur einen Theil der 
Stirnwand einnehmend.” 
Pergens, in 1890, abolished the Metopoporina, by separating it 
into two groups, the Ceina for the Ceidte, and the Melicertitina 
for what is practically the same as the Eleidae. According to 
Pergens, in the Melicertitina the zooecia are trumpet- shaped ; the 
aperture occupies only a part of the external surface of the zooecia ; 
and the ‘ ovicells ’ are interior, opening bj’ a triangular, elongated 
aperture. 
Of these successively proposed groups the Salpingina and 
Stigmatoporina are impracticable, as they include only the 
