JONESIELLA. 39 
pairs having both branches composed of three joints ; 
basal joint of the fifth pair very broad, second joint 
smaller. One ovisac. 
Seen from the side these animals have much the 
appearance of the genus Hctinosoma, the first body- 
segment being small and tapering towards the front, 
the abdomen also slightly tapering and extended per- 
sistently nearly in the axis of the cephalothorax; the 
structure of the swimming-feet is also very similar, 
but the mouth-organs are entirely different. I have 
much pleasure in naming the genus after my old and 
valued friend, Prof. T. Rupert Jones, one of the 
first and most zealous workers amongst the fossil 
Hntomostraca. 
1. JONESIELLA FusIFoRMIs (Brady and Lobertson). PI. 
XLVIII, figs. 1—13. 
Zosime fusiformis, B. & R. Brit. Assoc. Report, p. 196 (1875). 
Body elongated, slender; head and first thoracic 
seoment coalescent, produced into a slender rostrum. 
Anterior antenna 7-jointed, short, the last four joints 
short and densely clothed with long hairs (fig. 2), 
some of which are strongly pectinate or plumose; the 
fourth joint bears a long rod-like appendage (fig. 2 a), 
and the fifth a peculiar, branched, spine-like seta 
(fig. 2 6). In the male the antenna is irregularly 
corrugated, and has a large vesiculiform swelling of 
the fourth joint (fig. 3). Posterior antennz stout, 
and armed on the second joint with several short 
spines, some of which have pectinate margins (fig. 4), 
