686 Dr. T. A. Cliapman on Asymnutry in 



notice unless looked for. There is a well-developed sym- 

 metrical sheath, the mdceagiis itself is very long and very 

 slender, as in hoinlyyliformis, but though the opening is to 

 tlie right side the process beyond it is short and bhint, at 

 least viewed laterally, viewed dorsally it seems very sharp ; 

 in reality, it is merely the lip of the terminal opening, 

 prolonged on the left side. The ventral basal inflations 

 of the valves are much the same on both sides ; the left 

 one terminates in a rather sharp angle, with some bristles, 

 the right in a process like that of homhyliformis and 

 croatica, but by comparison ridiculously minute, so as to 

 be easily overlooked. The flat portion of the valve is 

 deeply emarginate on both sides, so as to present a long 

 slender strip, with a basal projection (tlie piece below the 

 emargination) on the ventral side. This basal projection 

 is much narrower on the left side. 



H. thyshe has a sheath symmetrical and even more fully 

 develQped than in fuciformis. The xdceagus is a little 

 more robust, has the opening to right side and a spine 

 continued a little beyond it, with a little flexure to the 

 left. Tlie basal bulla of the clasps is larger on the right 

 side, and has the terminal process on that side well de- 

 veloped, much for size as in homhyliformis, but straighter, 

 with a more slender shaft and more globular liead, armed 

 with quite long bristles on its dorsal side. On the left 

 side, the smaller bulla terminates in a short thimble-shapetl 

 process, not i as long as that on the other side ; it carries 

 a few bristles. On the right side the flat process of tlie 

 valve diminishes in width from about its middle. On the 

 left side, it begins to diminish close to the base, and the 

 valve is very narrow about 4 from the base and gets a 

 little broader again at the end. 



I may note here that I call the lateral movable pieces 

 valves or clasps. The flat expanded portion I so describe, 

 or call it valve simply. The knobs, hooks, spines, etc., 

 often double, that lie within this, basally and ventrally, 

 but always firmly soldered to it, so that they move 

 together, I call the harpe. The upper piece, with a single 

 or double spine above and another below the anus, I call 

 the tegumen. The central tubular piece of chitin I call 

 the /edceagus, reserving the name of penis for the eversible 

 membrane at the summit of this. There is often a mem- 

 branous, or even more or less chitinous sheath at the base 

 of the xdceagus; I call this the sheath. There have been 



