20 



between well divided groups based on structural diversities I prefer at present to 

 aclinowledge only a single genus, Meliceritites. The most significant structural di- 

 versity is to my opinion the presence or absence of an oral ledge, but when the 

 state of conservation is not a good one it is not easy to see whether the aperture is 

 provided with a feeblj' developed oral ledge or not. Also the diversities found in 

 the heterozooecia may perhaps be of systematic significance, but to decide tliese 

 different questions it should be necessary to possess a large and well-conserved 

 material. 



Meliceritites magnifica d'Orbigny. 



Multclea magnifica d'Orbigny, Brj'oz. crét, p. 649, pi. 740, figs. 1 — 9. 



Melicertites magnifica Pergens, Revision d. Biyoz. p. 397. 



Melicertites royana Waters, Annals Nat. Hist, [li] Vlll 1891, p. .51, pi. VI, figs. 2, 4-6, 11. 



Multelea magnifica Gregory, Cret. Bryoz. p. 31.6. 



(pi 1, figs. 3-10, pi. VII, figs. 13- 19.) 



The Zooecia which are divided by distinct marginal ridges are small and have 

 when freely developed a more or less regular rhombic outline, but in most cases 

 each zooecium is enclosed between two heterozooecia which greatly influence both 

 the size and the form of the subopercular area, and in the zooecia enclosed between 

 the proximal halves of two heterozooecia a large part of this area is covered by 

 the distal part of a proximal heterozooecium. No distinct tubercles. The aperture 

 which takes up the whole breadth of the zooecium in the distal part may be con- 

 tained two or rarely three times in the length of the zooecium, but in most cases 

 it is longer than the subopercular area. It is longer than broad, half-elliptical or 

 roundedly triangular and surrounded by a raised peristome, sometimes provided 

 with a small distal projection. The anter of the aperture is provided with a distinct 

 but rather narrow oral ledge, and the convex operculum which sometimes shows 

 a distinct flabelliform striation presents a more or less distinct triangular depres- 

 sion which from the proximal margin extends more or less far distally. 



The Heterozooecia which are much larger than the zooecia are of a lengthened 

 rhombic or hexagonally rhombic form with the four lateral margin more or less 

 incurved. The opercular area which ends in a rounded apex may be very much 

 protuding and obliquely ascending, and the inner aperture is concealed by a much 

 concave covering (the »lateral processes«) the proximal half of which is provided 

 with a narrow mediane fissure and the proximal margin of which by a similar 

 transverse fissure is divided from the more or less protuding somewhat thickened 

 distal margin of the concave subopercular area. The heterozooecia in this species 

 are much more numerous than in any other hitherto described. 



The Closure takes place in different ways. In many zooecia the aperture is 

 closed by a concave lamina but in others (figs. 6, 7) I have seen a closure-plate 

 of a similar appearence as the concave covering found in the opercular area of the 

 heterozooecia, namely presenting two narrow fissures forming right angles with each 

 other. Perhaps the latter form of closure is only the beginning of the concave 



