TRIARTIIllAD.E. 5 



expanding to a broad truncate margin. Beliind tliere is a great ovate opening, as if a 

 slice had been cut off the entire breadth from the middle to tlie extreme point. Doubt- 

 less this, in life,' is covered with membrane, and its edge is thickened. From the upper 

 margin rise two short setae, 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 is a 

 feather in appearance ; the shaft, moderately long and stout, being beset, on its two 

 opposite sides, with regular pinnules like those of a fern (Polijjjodiiim, for instance), in 

 considerable number, length, and regularity (fig. 9c). These pinniB 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 Rotifeea 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 Scaridium eiuJactijlotam. From the 

 condition of the lorica I have little doubt that *t had come to me alive ; but being occupied 

 with the new Scaridium I did not search closely. — P.H.G.] 



Length. Of lorica, y},-, inch ; to tips of pinnse, -5^3 inch ; from brow of lorica to tip of 

 ventral seta, J^- inch. Habitat. Loch near Dundee (P.H.G.). 



Genus TRIARTHEA, Ehrcnbcrg. 



GEN. CH. Spines single, two lateral, one central; eyes two frontal ; mastax of 

 vioderaie size ; trophi vialleo-raniate. 



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 cesophagus. The first of these characters is 

 one that cannot be much relied on except in the case of T. hrcviseta ; 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 tliat T. longiscta possesses this separation and that T. niystacina 

 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 shai'ply di-N ided into in- 

 testine and stomach. 



