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. 
OrtontA, Nicholson [1872]. 
Ortonia pseudopunctata, Vine. 
Ortonia conica, Nicholson, var. pseudopunctata, Vine, 1882, Quart. 
Journ. Geol. Soc. vol. xxxviii. p. 588, pl. xv. fig. 3. 
Tube regularly conical, attenuate, flexuose, adherent by one 
side; with numerous annulations. ‘he Gotland specimens 
measure 2 millim. in length. The present species seems to 
have intermediate characters between Ortonia minor, Nichol- 
son, and Ortonta conica, Nicholson. 
The specimens are adherent to Brachiopod shells. One 
example has a calcareous layer extending round the distal 
end of the tube. 
Silurian; Mulde, Gotland. Rare. 
ARTHROPODA. 
Clas ENTOMOSTRACA. 
Order OSTRACODA. 
The natural relationships of many of the genera of Paleozoic 
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 fossil forms of Ostracoda. 
The genera Thlipsura and A’chmina and also Primitiopsis 
are placed apart and after the family of the Cytheridee and 
before the Cypridide. Regarding the two former genera, 
Prot. Jones remarks :—‘‘ Their alliance is not yet clear, and 
they are in many respects peculiar.” He also says regarding 
Primitiopsis :— Related to the Cytheridez through the fossil 
Cytheridea, and to the Cypridide through the recent Chlamy- 
dotheca.”’ 
