part 3] THE KELESTOMINJS. 213 



to erect and cylindrical ; the cecia increase somewhat in size ; the 

 costae undergo a slight catagenetic decrease in number; and the 

 avicularia tend to become more pointed. These characteristics 

 mav be summarized in the following 1 tabular diagnosis of the three 

 sjjecies : — - 



1. Kelestoma elongation Marsson. Incrusting ; oecia about '75 mm. long' ; 



costse, 27 to 30. 



2. Kelestoma gmdatum, sp. nov. Erect, trilaminar; oecia about '9 mm. 



long; costas about 27. 



3. Kelestoma scalare Lang. Erect, cylindrical ; oecia about "9 mm. long ; 



costa? about 24. 



All these species occur in the Senonian, zone of Belemuitella 

 mucronata, on the island of Riigen. ■ 



Kelestoma geadatum. sp. nov. (fig. 8, p. 214). 



Diagnosis. — Kelestoma with an erect, bilaminar asty; cecia 

 about "9 mm. long; costae about 27. 



Distribution. — Senonian, Campanian, zone of Belemuitella 

 mucronata ; Riigen. 



Type specimen. — British Museum, D 15065. Agnes Laur 

 Collection. Since Kelestoma gradatum has not } r et undergone 

 published description, it is necessary to give it formal descriptive 

 treatment. 



V. Moephasmopoba Lang (figs. 10-12, pp. 215-17). 



Kelestoma diverged from the Primitive Kelestomine by greatly 

 lengthening the oecia and greatly increasing the number of costae. 

 The Primitive Morphasmopora may be imagined as remaining 

 comparatively squat in oecial shape, and but slightly increasing the 

 number of costae of the Primitive Kelestomine ; though carrying 

 the differentiation of apertural spines .to far greater lengths than 

 does Kelestoma. Besides, the avicularia of Morphasmopora are 

 primitively four in number (being two only in the Primitive 

 Kelestoma) accompanying the aperture of each normal (ec-ium — a 

 lowly, more proximal pair and a distal pair that during evolution 

 becomes carried high up on a pedestal to the level of the secondary 

 apertural rim; moreover, their apertures in Morphasmopora 

 brydonei are distally and obliquely directed away from the mid- 

 line of the aperture that they accompany, instead of towards it as 

 in Kelestoma, but proximally and obliquely towards the mid-line 

 in Morphasmopora jukes -brownei. Fig. 9 (p. 214) is a diagram of 

 the aperture of a lrypothetical Primitive Morphasmopora showing 

 these characters. In Morphasmopora jukes-brownei ( tig. 11, p. 21 6) 

 one pair of avicularia has been lost, and the single proximally- 

 directed pair is not so highly raised on the apertural rim. This 

 species is also catagenetic in the number of costae, possessing ten 

 only, whereas in M. brydonei they had increased to twelve from 

 the original ten of the Primitive Kelestomine. 



