THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE V. VOL. III. 



No. VII. — JULY, 1906. 



aiEixG-xisrj^iLj u^iaoricXiES. 



I.— Further Notes on the Stratigraphy and Fauna of the 

 Trimmingham Chalk. 



By R. M. Bkydone, F.G.S. 



(WITH 13 TEXT-FIGURES.) 



(Concluded from the March Number, p. 131.) 



BEFORE proceeding to the description of new species it may 

 perhaps be well to make a few remarks on the classification of 

 the Cretaceous Polyzoa and in particular of the Cheilostomata, the 

 suborder which embraces all the species I propose to describe. 



The main features of D'Orbigny's classification of the Cyclostomata 

 have been generally accepted, but his classification of the Cheilo- 

 stomata has sufiered very severely at the hands of subsequent authors 

 both in principle and in detail. It was based very largely on two 

 principles, one the generic importance of habits of growth, and the 

 other the generic importance of variations in the number and position 

 of the dwarfed avicularian appendages which he called ' pores 

 speciaux.' The latter principle has been entirely discarded by 

 recent authors, and with undoubted justice, as it involves the assump- 

 tion of the perfect regularity of the most irregular feature of the 

 Cheilostomatous cell. The application of the other principle and the 

 importance attributed to it have been gradually more and more 

 restricted, until we have reached a stage where it is still generally 

 admitted to hold good in the case of the Lunulitidse and Hippothoidse, 

 but on the strength of the behaviour of certain recent and Tertiary 

 species has been denied even specific importance in the other 

 Cheilostomatous families. It is time that a protest was entered 

 against this rigid application of conclusions drawn from Tertiary 

 and recent forms to the classification of Cretaceous forms. It is 

 unfortunately the case that D'Orbigny, by an oversight in applying 

 his principle in detail, laid it unnecessarily open to attack. It must 

 be obvious that even if the principle be fully accepted, the separation 

 which D'Orbigny made between the free and encrusting unilamellate 

 species, e.g., SemiescJiara and Cellepora, Semijliistrella and Repto- 

 flustrella, must be unsound. It is quite impossible to say that any of 

 the free unilamellate forms found in the Chalk greio free. Seaweeds 



decade v.— vol. III. — NO. VII. 19 



