146 Mr. F. Chapman on some 



Annulations numerous, about six to 1 millim. ; they are 

 somewhat irregular and have their edges broken up into 

 numerous closely-set tubercles. 

 Silurian ; Mulde, Gotland. 



Oetonia, Nicholson [1872]. 



Ortonia pseudopunctata, Vine. 



Orto7}ia conica, Nicholson, var. pseuchqntnctafa. Vine, 1882, Quart. 

 Journ. Geol. Soc. vol. xxxviii. p. 383, pi. xv. tig. 3. 



Tube regularly conical, attenuate, flexuose, adherent by one 

 side ; with numerous annulations. The Gotland specimens 

 measure 2 miUim. in length. The present species seems to 

 have intermediate characters between Ortonia minor, Nichol- 

 son, and Ortonia coriica, Nicholson. 



Tlie specimens are adherent to Brachiopod shells. One 

 example has a calcareous layer extending round the distal 

 end of the tube. 



Silurian ; Mulde, Gotland. Rare. 



ARTHROPOD A. 



Class ENTOMOSTRACA. 



Order OSTRACODA. 



The natural relationships of many of the genera of Palaeozoic 

 Ostracoda are more or less obscure. The following table of 

 the grouping, which has been kindly drawn up by our best 

 authority on the subject, Prof. T. Rupert Jones, F.R.S., 

 to whom I am indebted for many helpful suggestions in 

 writing this section of the paper, will be of the greatest use 

 to students of the lossil forms of Ostracoda. 



The genera T/ilipswa and j^chiuina and also Primitiopsis 

 are placed apart and after the family of the Cytherida3 and 

 before the Cypridida\ Regarding the two former genera, 

 Prof. Jones remarks : — " Their alliance is not yet clear, and 

 they are in many respects peculiar." He also says regarding 

 Primitiopsis : — " Related to the Cytheridae through the fossil 

 Cytheridea, and to the Cyprididse through the recent Chlamy- 

 dothecay 



