26 



G. 0. SAUS. 



[Xo. 1. 



a rather slender aud eloiigate muscle is seen extending from in 

 front to the base of each leg (see Pl. VIII, figs. 1, 4), apparently 

 representing the protractor, and several other shorter muscles 

 join the legs obliquely from behind, serving for the retraction 

 of the legs. Besides, a number of thin muscular bundles are found 

 traversing botn the endopodite and exopodite of the legs, being 

 partly, especially at the limit between the second and third seg- 

 ments of the endopodite, arranged in a radiating manner. 



d. The Tatt. 

 (Pl. v, fig. 5). 



This division of the body is composed of a single segment 

 only, containing within the terminal part of the intestine and 

 bearing at the extremity a pair of claw-like appendages. It 

 has the form of a rather broad somewhat compressed plate, of 

 an irregular triangled form, as a rule pointing inferiorly, or 

 even anteriorly, on account of the strong curvature of the poste- 

 rior part of the trunk. The ventral edge is quite smooth and 

 nearly straight, running out at the end into two small denticles, 

 placed side by side. The dorsal edge of the plate, generally turned 

 downward, is sharpened throughout the greater part of its length 

 and armed with a double row of seven to eight spiniform projections, 

 successively and rapidly increasing in size, the spines next to 

 the apex being very large and strongly curved, whereas the op- 

 posite pair are very small, and may be easily overlooked. All the 

 spines are finely denticulate on the posterior side, the denticles 

 being arranged rather irregularly, without forming distinct rows. 

 Besides, the ultimate and strongest pair of spines are armed at 

 the base with a regular series of about ten rather small secon- 

 dary spinules, finely denticulate along the posterior edge. At 

 the point where the above-mentioned double row of spines com- 

 mences, is seen on the dorsal side a small knob-like projection, 

 to which two slender biarticulate and finely ciliated setæ are 

 affixed, the so-called caudal setæ, which also occur in the same 

 place in the other forms belonging to the present group of 



