Correspondence — Prof. J. F. Blake — C. D. Sherhorn. 287 



distribution of the Lamellibranchia: 29 species are recognized, 

 six being new. The genera represented are : Leda, Nucula, Area, 

 Limopsis, Modiola, Iiioceramiis, Ostrea, Chlamys, Lima, Spondylus, 

 Flicatida, Cardium, Cardita, Arctica, Trapezium, Corhis ?, Martesia ?, 

 and Cuspidaria. 



In the concluding part the author compares the fauna of the 

 Beiissianum-zone (Chalk Eock) in England with that of other 

 European areas, particularly N.W. G-ermany and Saxony. In the 

 latter country the number of species in some groups — especially 

 Gasteropoda and Lamellibranchia — is much greater than in England ; 

 this dift'ei'ence is probably due to the sea having been of less depth 

 than in the English area. It is noticed that the species of Cephalo- 

 poda have a much wider geographical range than the other groups 

 of the Mollusca. 



Finally, by a study of the present distribution of those genera — 

 which form the predominating element in the fauna — taken in 

 conjunction with the other characters of the zone, the author arrives 

 at the conclusion that in England the Reussianum-zone was probably 

 formed between the depths of 100 and 500 fathoms. 



A CANTEONA UTIL US BISPINOS US. 

 Sir, — Mr. Foord will find the first cousin, if not the brother, of 

 his Acanthonautilus hispinosus^ figured in " Materiaux pour la 

 Palasontologie Russe," Tom. i, 1869, in Tab. v of a paper by 

 Golowkinsky on the Permian formation of the central part of the 

 Kama-Volga basin. It is there called Nautilus cornutus. 



J. F. Blake. 

 Geological Society, Buulington House, W. 

 April 12, 1897. 



ACANTHONAUTILUS: A CORRECTION. 

 Sir, — In the April number of the Geological Magazine appears a 

 description of Acanthonautilus as a new genus. As this has already 

 been published in Dr. Foord's Inaugural Dissertation (Mtinchen, in 

 1896), " Ueber die Orthoceren des Kohlenkalks [Carboniferous 

 Limestone] von Irland, etc.," the statement that it is new is likely 

 to mislead the student. C. Davies Sherborn. 



540, King's Road, London, S.W. 



April 26, 1897. 



Sir, — Since my paper on Acanthonautilus hispinosus appeared in 

 your April number, my attention has been directed to a work in the 

 Eussian language (" Material for the Geology of Eussia," vol. i, 

 1869), containing a paper by N. Golovkinsky, in which is figured 

 and described a species — Nautilus cornutus — closely related to mine, 

 though from a higher horizon, the Permian. From a study of the 

 figures it is clear that the species are quite distinct. Thus, in 

 A. bispinosus the shell expands rapidly, and has a broad and shallow 



1 Geol. Mag., April, 1897, p. 147, PI. VI. 



