2 DR. E. H. VINEN ON A CURIOUS FORM 
double, placed near the lateral margins and below the anterior 
third of the segment. Caudal segment furnished with twelve 
spines or sete, eight long and four short; the former being retro- 
verted and disposed in pairs, alternating with the latter, which are 
somewhat nearer the extremity. 
In addition to these characters, I may remark that the head 
appears to be supplied with a complicated buccal apparatus, but 
the preservative medium has rendered the parts so transparent 
that I refrain from hazarding a precise description of its several 
parts. Moreover, in different examples these appearances are dis- 
similar, whilst the cephalic segment itself is proportionally longer 
in some cases than in others. The eye-spots are always distinct, 
more or less elongated, each evidently consisting of two separate 
pigment-masses, the line of demarcation being clearly defined. 
In the specimen figured a on the slide, the eyes are much more 
elongated and more uniform in outline ; being, nevertheless, thicker 
behind than in front. Connected with the eyes and buccal appa- 
ratus there are two laterally disposed muscular masses, which 
almost fill up the longitudinal halves of the cephalic segment. 
The buccal cavity itself is tolerably well defined, being funnel- 
shaped and apparently closed behind. The cesophagus takes its 
origin at the upper and back part of the sac, immediately behind 
a peculiar form of dental apparatus which guards the pharyngeal 
opening. This structure forcibly reminds one of the gastric teeth 
found in decapodous Crustaceans, and appears to consist of a 
central and two lateral horny pieces, which, acting upon one 
another, serve to comminute the food only partially broken up 
by the buccal organs. The intestinal canal can be traced through- 
out the entire series of segments, and on either side of it runs a 
conspicuous vessel filled with highly coloured blood. I have not 
observed any trace of reproductive organs, a circumstance which 
alone renders it highly probable that we have to do with a larval 
insect. The last or thirteenth segment is considerably narrower 
than those of the body proper. The eight Jong spines are jointed 
at the base, where they are comparatively thick, becoming gradu- 
ally attenuated towards the tip ; the segment itself is also slightly 
increased in breadth at the lower end. The length of each spine 
is somewhat less than that of the caudal segment, and fully four 
times longer than those of the smaller series placed nearer to the 
end of the segment ; these latter project at a right angle from the 
tip, and do not appear capable of retroversion. 
