330 
MELICERITITES. 
PI. XIY. Pig. 3. Part of a worn branch, X 10 dia. Upper 
Greensand: Warminster. Cunnington Coll. 60,539. 
Pig. 39. Part of a zoarium, x 18 dia. Cenomanian: Essen. 
Old Coll. D. 7093. 
Fig. 39. — snmclansa (Mich.). 
Affinities. 
The synonymy of this species is a little complex, for on the 
basis of zooecial measurements M. Pergens has excluded from it 
the specimens refeiTcd to it by d’Orbigny, and included in it some 
specimens with large apertures from a higher horizon. M. Canu 
has followed Pergens’ lead. 
But this proposal is based on an inversion of the characters in 
the two species, viz., the attribution to M. semiclausa of larger 
apertures than those of M. gracilis^ in which Pergens and Canu 
include the M. semiclausa of d’Orbigny. Thus Pergens states the 
width of the aperture in M. semiclausa (Mich.) as *22 mm. and 
in M. gracilis as *12 mm. But that Michelin’s gracilis (i.e. 
cenomana, Orb.) had larger apertures than his semiclausa is clearly 
stated in his diagnosis; thus of the former he says: “ostiolis 
approximatis, ovatis, majusculis, partim diaphragmate dirisis”; 
M. semiclausa^ on the contrary, he describes as “ostiolis, minimis, 
rotundis, saepe obstructis, in lineas circulares, distantes, prominulas 
dispositis.” Michelin’s figures are in agreement with his text, 
and specimens in the Tesson Collection show that the characters 
occur as defined. 
The M. cenomana^ Orb., is the Cenomanian form of M. semiluna^ 
and Jf. semiclausa is probably the Cenomanian form of M. undata. 
The separation of the two Cenomanian forms does not seem 
practicable on measurements alone : thus, whereas Pergens states 
that the width of the aperture in M. gracilis is ‘12 mm., Canu 
