23 



Meliceritites angulosa d'Orbigny. 



Nodelea angulosa d'Orbigny Bryoz. crét. p. 610, pi. 735, figs. 4— 5 (non 6). 



— ornata d'Orbigny op. cit. p. 612, pi. 736, figs. 12—16. 



— transversa d'Orbigny op. cit. p. 613, pi. 736, figs. 5— 8. 



— pulchella d'Orbigny op. cit. p. 613, pi. 736, figs. 1—4. 



— ogivalis d'Orbignj' op. cit. p. 624, pi. 737, figs. 8—10. 



— scmiclausa d'Orbigny op. cit. p. 619, pi. 678, fig. 7, pi. 736, fig. 16. 

 Multinodelea tuberosa d'Orbigny op. cit. p. 615, pi. 736, figs. 9-11, 13 — 15. 

 Melicertites undata Gregory (non d'Orbignj') op. cit. p. 340, pi. XV, figs. 3, 4, pi. XVI, fig. 3. 



(PI. 11, figs. 4-22.) 



The Zooecia which are divided from each otlier by more or less developed 

 marginal ridges are in most cases of a more or less distinct hexagonal form, and 

 the semielliptical aperture is always provided with a distinct, but more or less de- 

 veloped oral ledge, and with a distinct peristomial thickening. It takes up in most 

 cases the whole breadth ot the zooecium in the distal part; but while in some cases 

 it is longere than the subopercular area in others it is shorter, and sometimes its 

 length may be contained twice in the length of the latter. More or less developed 

 tubercles. The operculum is convex and provided with radiating striae. 



The Heterozooecia which are present in very sparse number and are very vari- 

 able in form and size are dispersed singly or in pairs among the zooecia which 

 they always surpass in length. Most of tiiem have about the double length of the 

 zooecia, but sometimes they are only a little longer. In opposition to the hetero- 

 zooecia of Mel. magnified and Mel. trifoliuin the inner aperture is always visible, not 

 being concealed by »lateral processes«, but the form of the opercular area is subject 

 to a very great variation, being dependent not only on the different relation be- 

 tween its length and its (largest) breadth, but also on the form of the lateral mar- 

 gins, and lastly on the manner in which the latter run together to form the distal 

 end of the area. The relation named varies between 4:3 and 5:2, and the lateral 

 margins may sometimes in the greater part of their length be parallel or allmost 

 so, sometimes more or less convergent and sometimes more or less incurved. As 

 to the last named difference the lateral margins run together to form an almost 

 semicircular curve while in other cases they make an almost rectangular bend in 

 ordre to form the feebly curved distal end. Also the relative length of the oper- 

 cular- and the subopercular area is subject to variation, and the former may some- 

 times be three times as long as the latter while in other cases it is only a little 

 longer. In most cases it attains the double length. In a number of heterozooecia 

 I have found an arched calcareous mandible whicJi sometimes shows a similar 

 striation as that found in the operculum. 



Kenozooecia have not been found. 



The Ooecia are of different form and size. 



The Closure of the zooecia is effected by a concave lamina starling from the 

 free edge of the oral ledge and developing in such a way that at a certain point 



