The President's Address. By Henry Woodward. 151 



from the Lower Cambrian of North America. Capulus lias per- 

 sisted from Cambrian times to the present day. 



The remarkable genus Pleurotomaria also ranges from Cam- 

 brian to recent, living in Japan and in the West Indies, and is re- 

 presented by 4 or 5 species recent; 11 Tertiary; 575 Secondary ; 

 and 570 Palaeozoic forms. 



The Nerineidce are very specialised shells in the structure of 

 the columella ; their range is also very brief. There are 150 species 

 recorded from Mesozoic strata. 



The Pulmonifera, Land-Snails range from the Coal Measures 

 to recent. 



Among the Cephalopoda, the Nautlloid type is remarkable for 

 its persistence since Cambrian times. Many specialised forms, 

 showing extreme variety of growth and shell-structure, have 

 branched out from this stock during its dominance in Palaeozoic 

 times, but these have in turn all died out. 



Of these, the simple genus Orthoceras, with its long straight 

 shell, had the greatest range, viz. from the Cambrian to the Trias ; 

 the other modifications have also fairly long ranges and show re- 

 markable varieties of shell-structure. 



The Ammonites, which range from the Trias to the Chalk, show 

 almost endless variety in shell-ornament within certain limits, 

 and have a world-wide range in Jurassic times branching out 

 into more than 600 species. 



In the Cretaceous period (before their disappearance) they put 

 on most singular and remarkable developments of shell-variation, 

 Crioceras, Scaphites, Ancyloceras, Helicoceras, Toxoccras, Baculitcs, 

 Ptychoceras, Hamites, Turrilites, then they disappear entirely. We 

 •do not know the animal in Ammonites. 



The Bclemnitidcc range from the Trias to ths 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 and the 

 guard 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, Yorkshire, Lyme, in Dorset- 

 shire, and other localities in the central counties. More than 100 

 species have been described. 



Possibly Sjrirulirostra, 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* 



The following table shows the range of the Arthropoda in 

 time. 



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

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

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



