TRIARTHRAD As. 5 
expanding to a broad truncate margin. Behind there is a great ovate opening, as if a 
slice had been cut off the entire breadth from the middle to the extreme point. Doubt- 
less this, in life, is covered with membrane, and its edge is thickened. From the upper 
margin rise two short sete, jointed to knobs; while from the breast, exactly opposite, 
there issues another, similarly jointed but of great length, descending far behind the 
extremity of the body. 
But the chief peculiarity of the creature is that four-and-twenty styles, regularly 
arranged, are affixed to the lorica, giving a most unique aspect to it. For every one isa 
feather in appearance ; the shaft, moderately long and stout, being beset, on its two 
opposite sides, with regular pinnules like those of a fern (Polypodiwm, for instance), in 
considerable number, length, and regularity (fig. 9c). These pimne are arranged in 
six longitudinal rows, three on each side, on the ventral aspect, the middle pair of 
rows consisting of six each, the next pair four, and the outmost two, each. The shaft of 
each is evidently articulated on a knob of chitine, which is itself a tubercle on a some- 
what larger round knob, set in a commensurate orifice in the lorica,—apparently moving 
freely in it, a true ‘ ball and socket ’’ joint, worked doubtless by proper muscles within. 
Thus, adding the three simple styles, which are similarly based, we have here a wonderful 
array of exterior articulate members, which well illustrate the claim of the RorirERa to 
a place among the ARTHROPODA. The pinnules vary much in their number, their 
length, and the angle of their expansion. The body ends in a blunt point, with no foot, 
nor other appendage. The anterior extremity, beyond the marked neck, is short, some- 
what inclined toward the back, truncate, with an orifice as wide as the widest part of 
the trunk. Through this, of course, the head is protruded during life; but of this, and 
of the whole internal organization, I can give no information. The specimen which 
came under my observation was an empty lorica, in good preservation, as if recently 
dead, which I was enabled to revolve under the microscope, and so to examine in several 
aspects. The whole lorica was of a dark yellow-brown hue, with a dull translucency 
like that of a smoky horn lantern: but whether this is specific, or only accidental, I 
cannot tell. 
This most curious form occurred in the sediment of a bottle of water, examined on 
October 20, 1885, but which had been standing on my table since September 23, when 
I had received it from Mr. Hood with a colony of Scaridiwm eudactylotum. From the 
condition of the lorica I have little doubt that it had come to me alive ; but being occupied 
with the new Scaridiwm I did not search closely.—P.H.G.] 
Length. Of lorica, +}, inch; to tips of pinne, ,); inch; from brow of lorica to tip of 
ventral seta, 7; inch. Habitat. Loch near Dundee (P.H.G.). 
Genus TRIARTHRA, Ehrenberg. 
GEN. CH. Spines single, two lateral, one ventral; eyes two frontal ; mastax of 
moderate size; trophi malleo-ramate. 
There are three known species of this genus, and they resemble each other very 
closely ; the main points of difference being the length of the leaping-spines, the distance 
between the eyes, and the length of the esophagus. The first of these characters is 
one that cannot be much relied on except in the case of 7. breviseta ; for the length of 
the spines varies very much in the same species. Ehrenberg makes a further point of 
difference, in the presence or absence of any well marked separation between the stomach 
and intestine, asserting that 7’. longiseta possesses this separation and that 7’. mystacina 
lacks it. This, however, is a character of small value, for the same animal will show at 
one time an undivided alimentary canal; and, at another, one sharply divided into in- 
testine and stomach. 
