EEPOET ON THE ANNELIDA. 
59 
form, there is here a wide area, wdiich probably represents a further stage of the diverg- 
ence from the common type. Instead of the fairly formed head of I'pliione muricata, it 
is difficult to say which is the essential cephalic region in this form. The head presents 
posteriorly a median fissure flanked on each side by a large soft tubercle, which may aid 
in supporting the scale. A somewhat triangular area, with the broad base in front, 
completes the snout, the rounded anterior edge (which appears to be buccal rather than 
cephalic) folding over directly into the mouth. Inferiorly the scoop-like ventral lip projects 
considerably in front of the cephalic brim just mentioned. The broad j^osterior tubercles 
of the head narrow as they run forward, and end in a slight enlargement, which in the 
specimen shows no decided trace of an antenna. The palpi are comparatively short, 
tapering from base to apex, which is filiform. They arise beneath the posterior tubercles 
at each side. Between the first bristled foot and the latter is a sickle-shaped flattened 
lamella (corresponding to the first foot) bearing the tentacular cirri, which are short and 
filiform. The lamella is slightly enlarged at the tip, especially inferiorly. No trace of 
eyes occurs in the specimen. The great modification of the first foot (bearing the 
tentacular cirri) affords a marked contrast with I'pliione 'muricata. In both, however, 
the mouth opens C[uite in front, and thus differs from the ventral position of the organ in 
Lepidonotus. 
The scales are thirteen on each side. The first (PI. IX. fig. 5) is somewhat ovoid, the 
rest are more or less elongated (fig. 6), narrower internally, wider externally, and with 
a well-marked median curve. The posterior and outer angle is rather acute in the 
posterior scales. The surface of attachment is unusually large and firm. The structure 
of each areola respectively in Iphione muricata and this species differ, the former present- 
ing (when the scale is viewed as a transparent object) an arrangement like the cells in 
cork, the latter having a larger amount of chitinous tissue in the intersecting walls of the 
spaces. The outer margin bears a series of well-marked cilia, which in the first scale pass 
nearly all round. Along the anterior margin of this scale also there is a tendency to the 
grouping of the cilia on a basal web or pedicle, which shows a bifid, trifid, or other sub- 
division at the tip. Moreover, the homology of the spaces in the areae is indicated by 
their transition into spines in the same scale. The scales are brittle, and fracture seems 
always to take place along the junctions of the more or less hexagonal areae. The scar 
for the attachment of the scale does not exhibit the well-marked accessory process 
externally, so characteristic of Iphione muricata.. In vertical section the scales present 
a beautifully regular series of thin chitinous septa, which run from the surface to the 
base. Each of the little areas of the rounded dorsal papillae is thus mapped out. 
The dorsal division of the foot bears a dense tuft of light coloured hairs, which are 
considerably shorter than the ventral bristles, so that the latter constitute the prominent 
points along the sides of the body, whereas in Iphione muricata these are formed oy the 
dorsal bristles. Part of this prominence, however, is in the present species due to the 
