ROEMER — AIX-LA-CHAPELLE SANDS. 



19 



Base of the 

 calyx formed ■ 

 of three basal "^ 

 pieces. 



Mouth 

 lateral, 



excen- 



tric. 



tabular arrangement of the genera which form with it a natural 

 group or family. 



Base of the calyx formed of four basal pieces .... Melocrinus. 

 "Mouth at the summit, and central Actinocrinus. 



Plates of the calyx top 



all similar Amphoracrinus. 



Plates of the calyx top 

 dissimilar, five larger 

 ones above the arms 

 and an excentric one 

 over the mouth pro- 

 duced into long spines Dorycrinus. 



The author remarks, also, that some other Crinoids bear spines, 

 such as Acanthocrinus (from the Posidonomya-schist of the Hartz), 

 Jahrb. 1850, p. 679. t. 6, B. 



[T. R. J.] 



On the Cretaceous Sands o/'Aix-la-Chapelle. 

 By Dr. Ferd. Roemer. 



[Neues Jahrb. f. Min. u. s. w. 1854, pp. 167, 168. In a letter to Prof. Bronn, 

 Jan. 1854.] 



In the past autumn I had the advantage of a renewed examination 

 of the Aix-la-Chapelle district. With regard to the age of this cre- 

 taceous formation, I have not found occasion to offer any essential 

 modifications of the opinion I published several years since (Jahrb. 

 1845, p. 385-394), even after seeing the large collections of organic 

 remains since made chiefly by Dr. Jos. Miiller and Dr. Debey. 

 Indeed I feel convinced now, as I did then, that all these Aix creta- 

 ceous deposits belong to the Stage senonien of D'Orbigny, and that 

 none of them are so low down as the horizon of the planer. 



Passing over the many assertions of the occurrence of the Gault, 

 the Neocomian (Lower Greensand), or indeed of the Wealden at 

 Aix-la-Chapelle, — assertions which entirely rest on mere lithological 

 similarities, and are destitute of palseontological support, — I need 

 only notice the opposite view, according to which the Sand of the 

 Aachen- Wald and of Lonsberg, or at least a portion of it, should be 

 paralleled with the well-known fossiliferous beds of Blackdown, in 

 England. 



It is not denied that at first sight this latter parallelism attempted 

 by Dr. Jos. Miiller appears to have much value. The condition of 

 the fossils of the Aix sand in one locality fortunately discovered by 

 Dr. Miiller, in the neighbourhood of Vael, is similar to that of the 

 Blackdown fossils as to their metamorphism ; and a suite of Gaste- 

 ropoda and Acephala is very nearly analogous to a series from Black- 

 down. 



