THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE V. VOL. IX. 



No. IV.~APEIL, 1912. 



I. XOTES ON NEW OR IMPEKFECTLY KNOWN ChALK PoLTZOA. 



By E. M. Beydone, F.G.S. 



[Continued from the January Number, p. 8.) 

 (PLATE VII.) 



ONE of D'Orbigny's subsidiary methods of classification was to 

 create separate genera for those species which heap layer upon 

 layer of zooecia by prefixing ' Mtilt ' or ' MuUi ' to the name of the 

 genus to which they would but for this habit of growth be referred. 

 It is rather surprising that he did not have occasion to create a genus 

 Multeschara, as there are two species in the English Chalk which he 

 could only have dealt with in this way. They are of interest in their 

 bearing on the question of the admissibility of methods of growth in 

 classifying the Cheilostomata, as they are linked together by a most 

 adventitious peculiarity in growth and one which does not involve any 

 zooecial modification. They offer therefore a case in which, if those 

 who will not allow to zoarial growth any measure of classificatory 

 value are right, it might be anticipated that species so linked together 

 would be a heterogeneous assembly and not even consistent in this 

 liabit of growth. Such an anticipation would hardly be borne out in 

 the case of the English Chalk. The Multescharine habit is practically 

 confined to the two following species, which are most distinctly 

 homogeneous, and neither of which, as far as my experience goes, 

 ever adopts any other mode of growth (except for occasional specimens 

 of Rhagasostoma palpigerum of purely Escharine habit, which may 

 fairly be regarded as cut off prematurely in the Escharine stage, 

 through which every ' Ihdteschara ' must pass). The only other 

 Escharine species which I have ever found in Multescharine habit is 

 the very common form usually labelled JEseliara (or Onycliocella or 

 Bhagasostoma) Lamarclci, Hag., but which I strongly believe to be the 

 original Eschara irregularis^ Hag.,^ although neither the figure nor the 

 description is conclusive. After a severe struggle for existence in 

 the zone of Terebrattdina lata this species rapidly becomes abundant 

 in the Senonian stage, and in its vigorous youth in the zone of 

 Holaster planus it frequently assumes a Multescharine habit ; but this 



^ Hagenow, Jahrbuch filr Mineralogie, 1839, p. 264, pi. iv, fig. 2. 

 DECADE V. — VOL. IX. — NO, IV. 10 



