180 Geological Society. 



PROCEEDINGS OF LEARNED SOCIETIES. 

 GEOLOGICAL SOCIETY. 



June 5th, 1918.— Mr. G. W. Lamplugh, F.R.S., 

 President, in the Chair. 



The following communication was read : — 



'The Kelestoniinse, a Sub-Family of Cretaceous Cribrimorph 

 Polyzoa.' By William Dickson Lang, M.A., F.G.S. 



The Kelestominse are a sub-family of Pelinatoporidae. The 

 latter are a family of Cretaceous cribrimorph Polyzoa, whose costae 

 are prolonged upwards as hollow spines from the median area of 

 fusion of the intraterminal front-wall. The broken ends of these 

 spines form a row of pelmata (or, if small, pelmatidia) on the 

 intraterminal front- wall. 



The Kelestominse are Pelmatoporidse with an apertural bar each 

 half of which is bifid ; and the proximal and distal forks of each 

 half are fused with the corresponding forks of the other half. 

 The fused distal forks are also fused with the proximal pair of 

 apertural spines, which are greatly enlarged. 



The simplest known form of this arrangement is seen in the 

 genus Kelestoma Marsson. Kelestoma is characterized among the 

 Kelestominse by its great oecial length, and by the great number 

 of costse. Kelestoma has the following three species, which form 

 a single lineage : — (1) Kelestoma elongatum Marsson, with an 

 incrusting asty ; (2) a new species, with a bilaminar, erect asty ; 

 (3) K. scalare Lang, with an erect, cylindrical asty. There is, in 

 this series, a slight catagenetic decrease in the number of costse, 

 and the avicularian aperture becomes somewhat more pointed. The 

 genus occurs in the Senonian, zone of Belemnitella mticronata, in 

 the island of Riigen. 



Morphasmopora, unlike Kelestoma, retains a small number of 

 costse and a short ceciuin ; but the thickness of the proximal 

 apertural spines, which are hardly recognizable as such, is enormously 

 increased ; the thickness of the bifid apertural bar is also increased. 

 In Morphasmopora brydonei Lang, there are four circum-apertural 

 avicularia ; and the proximal apertural spines and the apertural bar, 

 though enormously developed, are not so large as in M.jukes-broivnei 

 (Brydone). The latter species has fewer costse than the former, 

 and but one pair of circum-apertural avicularia. There are also 

 differences in the interoecial and interstitial secondary tissue of 

 the two species. M. brydonei occurs in the island of Riigen and 

 M. jukes-broionei at Trimingham ; both from the Senonian, zone 

 of Belemnitella mucronata. 



