380 Reports and Proceedings — Royal Microscopical Society. 



The Belemnitidge range from the Trias to the Cretaceous. The 

 guard in most genera is large and dense, whilst the chambered 

 portion, or ' phragmocone,' is small and rudimentary. But 

 Aulacoceras of the Trias has a large phragmocone, the gudxd 

 being quite small. 



The Belemnites appear to have been gregarious (like their modern 

 congeners the 'Squids'), entire beds in the Lias being composed of 

 their guards at Whitby in Yorkshire, Lyme in Dorsetshire, and other 

 localities in the central counties. More than 100 species have been 

 described. 



Possibly Spirulirostra, of the Tertiaries, and the recent Spirula 

 may be survivors which have gradually dispensed with the guard to 

 the shell, so characteristic of the Belemnites proper.^ 



IX. — The following table shows the range of the Arthropoda 

 in time : — 



ARTHROPODA. 



A.— CRUSTACEA. 



Order 1 



(1) Bkanchiopoda. 



I. ENTOMOSTRACA. 

 Phyllopoda. 



Apus... 



2. Phyllocauida. 



Symenocaris, Ceratiocaris (Nbialia^) 



JEstheria 



Cheirocephalus 



Artemia 



3. Cladocera. 



Daphnia and its allies 



(The EpMppia Avinter eggs of Daphnia have been found fossil by 

 Mr. Clement Eeid, F.E.S., in the Forest Bed series of JSTorfolk.) 



4. OSTEACODA. 



Gypris, Canclona, Cythere, etc. ... Palaeozoic to recent. 



5. COPEPODA. 



Cyclops, eic Not found fossil. 



Many other families are not represented in a fossil state. 



II. MALACOSTEACA. 



Cambrian to recent. 



Ditto. 



Devonian to recent. 

 Tertiary to recent (fresh- water) 

 Ditto (saline). 



Probably all recent. 



1. PODOPHTHALMA. 



Brachyura . 

 Macriira 

 Sclnzopocla 

 Stomapoda 



2. Edeiophthalma. 



Gumacea 

 Isopoda 

 Frcearcturus . 

 Amphipoda . 



III. 



Trilobita 

 Merostomata. 



JSurypterida . 

 Xiphosura 



Jurassic to recent. 

 Carboniferous to recent. 

 Ditto (Palceocaris). 

 Devonian or Silurian to recent. 



Carboniferous to recent. 

 Magn. L. to recent. 

 Devonian (?). 

 Carboniferous (?) . 



GIGANTOSTEACA, Haeckel. 



Cambrian to Carboniferous. 



Ditto. 



Silurian to recent. 



1 I am desirous to mention here that for the above summary, from the Protozoa to 

 the MoUusca, I have largely made use of Mr. C. B. Crampton's statistics with some 

 modifications from my own notes and other sources of information. — H. W. 



^ Eecent analogue. Probable progenitor of Decapoda. 



