372 Bevieics — Development of Bacnlites. 



fi Trigonin gibbosa' : this contains Ammonites boloniensis and other 

 characteristic fossils, also Cyrena Peiluti, and Cidaris Jlorigemma] 

 (? derived). Conglomeratic and remanie beds occur at several 

 horizons from the base of the ' Marne a Perna Botichardi ' and 

 upwards, so that locally some of the Upper Portlandian horizons 

 are absent : and such beds would account for the preservation of 

 Cidaris florigemma. 



The highest Portland Beds are covei'ed in places by sands and 

 sandy limestones with Cypris, and by concretionary limestone with 

 A^tnrte sociatis and Candona bonoidensis. These belong to the 

 Purbeck Beds, which are grouped with the Wealden Beds, as 

 Wealden-Purbeck. Sometimes the Purbeck Beds rest on lower 

 ' assises ' of the Portland Beds. 



The Wealden Beds which comprise sands and greenish sandy 

 clay are conglomeratic and rest in places directly on Portland Beds. 



The Cretaceous Beds (grouped under the unfortunate term 

 ' Infracretace ') include (1) Ferruginous sands and gravel, and white 

 clays, with Ostrea Leymerii and Terebratula {Zeilleria) pseudojnrensis ; 

 and (2) grey or green sands with Ammonites mamillaris, and also 

 ferruginous and phosphatic nodules. 



These two divisions are grouped as Aptian. while the overlying 

 clays with Aminonites splendens, A. lautus, A. ivjlatus, etc., are grouped 

 as Albian or Gault. 



The unconformities previously noted are minor and local com- 

 pared with the great discordance between these Cretaceous beds and 

 the underlying strata; for they rest indifferently on the several 

 Jurassic stages, on the Carboniferous, and on the Devonian rocks. 



The following species are described and figured : — Athyris Beten- 

 courti, Givetian ; Spirifer Barroisi, Ehynchonella Le Meslii, CJwnetes 

 Douvillei, Limanomya Grayiana, Bouchard, L. rauUicostata, Bouch. 

 MS., and L, lineolata, Bouch., Frasnian ; Cyrtina Lonquetii, Carboni- 

 ferous ; Trigonin Seeleyi, Bathonian ; Ehynclioiiella Pellati, Opis 

 Pellati, Delphimda Parlieri, and Oncospira Legayi, Oxfordian. 



H. B. W. 



III. — The Development of the Shell in the coiled stage of 

 Baculites compressus, Say. 



LAST year Mr. Amos P. Brown announced ' the discovery of the 

 young of Bacidites rompressus, Say, in some Cretaceous marl 

 from near Deadwood, South Dakota, and showed that the genus 

 Bacnlites was coiled in its earlier stages, the coiled stage of B. com- 

 pressus consisting of two to two and one-half whorls and having 

 a diameter of 0*8 to 1 mm. By breaking the shell back from the 

 straight portion to the protoconch, Mr. Brown has now been able to 

 trace out the development of the coiled portion of the'shell.^ 



The protoconch is ellipsoidal, wider than high ; it is wider than 

 each of the succeeding whorls, and therefore when the coiled portion 



1 Proc. Acad. Nat. Sci., Philadelphia. 1891, pp. 159-160, woodcut. Noticed iu 

 this Magazine, New Series, Dec. III. Vol. VIII. 1891, p. 316. 

 a See Proc. Acad. Nat. Sci., Philadelphia, 1892, pp. 136-141, pi. ix. 



