4 
ON A NEW SPECIES OF ENTEROPNEUSTA, 
this is found the typical ring furrow forming the fourth region 
[figs. 1 and 15 (4)], and this is separated from the trunk by a 
narrow projecting circular rim— the fifth region — which forms the 
posterior boundary of the collar, and is somewhat wider than the 
succeeding trunk section. The collar may reach a length of 
9 mm. with a transverse breadth in the third region of 9 mm. 
also, so that in the living animal the collar may be said to be 
about as broad as long, but in preserved specimens the transverse 
breadth, owing to the strong contraction of the longitudinal collar 
musculature, considerably exceeds the length, and also the ventral 
length slightly exceeds the dorsal. 
Trunk. 
( 1 ) B 1 r an chio genital Region; This region may reach a length 
of from 36 to 40 mm. and a breadth of 7 mm. Ft. austra fieri sis 
is especially characterised by the great development of the genital 
wings — the duplications of the dorso-lateral regions of the body in 
which the gonads are situated — and in this respect the species is 
to be associated with Pt. aperta, clavigera, gigas, and aurantiaea y 
in Spen gel's provisional genus Tauroglossus. The anterior ends 
of the wings are continuous with the posterior rim of the collar, 
and immediately behind the latter their free edges may either 
slightly overlap each other or they may be infolded, and the wings 
then are in contact in the median line by their outer surfaces. 
The wings continue posteriorly in this condition and reach their 
maximum size somewhat posterior to the gill region. This con- 
dition is retained, in a slightly varying degree in different 
individuals, to within a short distance of the most anterior 
liver sacs, which are more or less completely hidden from view by 
the wings. Beyond this point the wings decrease rapidly in size 
and form two ridges lying at first laterally to the liver sacs but 
which are finally covered by the outer overhanging ends of the 
larger liver sacs (fig. 24, gw.), and which disappear altogether in 
the posterior part of the hepatic region. 
When the wings have the position just described no part of 
the gill area is visible externally, and the most anterior small liver 
