Recent Nautilus Research Articles

Variation of strontium content within shells of recent Nautilus and Sepia.

OUR survey of the strontium content of aragonite shells from living and fossil cephalopods1 has prompted us to make a more detailed study of the variations of strontium concentration within individual shells of two familiar species now extant—Sepia officinalis and Nautilus pompilius. Preliminary analysis revealed marked difference in the strontium content of the dorsal and ventral components of the aragonite sepion or cuttlebone of Sepia, and so we have investigated in detail samples of these specimens from different parts of the two components of the shells. Most of this communication is, however, concerned with the analyses of samples from two specimens of Nautilus. Altogether we have made 350 determinations of strontium, using an X-ray fluorescence technique1. All samples were analysed in duplicate and the precisional error ranged from ±1.8 to ±2.5 per cent.

Environmental significance of dwarfed cephalopods

Abstract Dwarfed and/or small cephalopods have been recorded from many parts of the geologic column. Data assembled from preliminary studies of the Cretaceous pyritic micromorph faunas of Texas and from an Upper Triassic (Norian) fauna from the Cordillera Central of northern Peru will be given. Both of these faunas contain an abundant cephalopod assemblage, mostly small in size, which are associated with other dwarfed and non-dwarfed invertebrates. Students of cephalopods are handicapped by the relative small amount of environmental data known on recent Nautilus. Some qualitative data on the environmental relationships of fossil cephalopods is known but practically no quantitative data is available. It is suggested that evolution has probably been an important factor in causing the development of some groups of small cephalopods.

IV.—Shell-Structure in the Ammonoidea

The shell-structure of the Ammonoidea has received very inadequate attention from palæontologists; in most cases authors are content with describing the shell of the recent Nautilus, and saying that that of the Ammonites is exactly the same. Prof. Judd therefore suggested that I should take the subject up, when working as a research student under him. As a result, I have found that the resemblance of the Nautilus- to the Ammonite-shell is literally true; but the structure of the extinct forms throws an altogether new light on that of the recent one, while the usual homology of parts between the two requires, I think, revision.

XXXI.—On the muscular impressions of some species of Carboniferous and Jurassic Nautiloids compared with those of the recent Nautilus

XXXI.—On the muscular impressions of some species of Carboniferous and Jurassic Nautiloids compared with those of the recent Nautilus