HEMIPODUS MEXICANUS. 349 



Hemipodus MEXICANUS, sp. nov. 

 Plate 63, fig. 2, 3. 



The general color at present is dusky grey-brown, with a somewhat darker 

 niiddorsal line evident in parts. The parapodia are lighter, more yellowish, 

 and the setae are colorless. 



The type is incomplete caudally. In its present condition it is about 29 

 mm. long and counts nearly fifty-five somites, the precise number not being 

 determinable because of the worn and frayed condition of the posterior region. 

 The greatest width, which is a Httle in front of the middle of the fragment, is 

 2.8 mm. From this region the body narrows conspicuously both cephalad and 

 caudad, the posterior narrow region being more slender and longer. 



The prostomium has its base sunk into the anterior end of the body, than 

 which it is very much more slender. It is slenderly conical, with the distal end 

 curving somewhat ventrad. Because of the insinking of the head in the type 

 the precise number of annuh cannot be satisfactorily determined, but it seems 

 to be eight or more. The tentacles are colorless and small, much less than the 

 median diameter of the prostomium. 



The somites are strongly convex both dorsally and ventrally, the transverse 

 diameter not much exceeding the dorsoventral one. There is no distinct neural 

 groove, though slight furrows set off a midventral neural region. All somites, at 

 least of the anterior and median regions, distinctly three-ringed. 



The parapodia at the anterior end are situated clearly below the middle 

 level of the sides, rising higher caudad. The first two pairs in the type are 

 directed forwards, the others sublaterad. Parapodia are uniramous, short, 

 and subcylindrical. Each at the distal end with two presetal ligulae, these slen- 

 derly cylindroconical, long, contiguous at base, with the dorsal one a Uttle longer 

 than the ventral. The postsetal ligula is single, proximally broad, but much 

 shorter than the presetal ones. The neurocirrus is situated on the ventral sur- 

 face near the middle of the parapodium in the anterior ones, further proximad 

 caudad; it is conically pointed and short, in no case exceeding the tip of the 

 postsetal process and in most falling clearly short of attaining this. The dorsal 

 cirri are situated on the side of the somites considerably above the bases of the 

 parapodia; they are very small cylindiical tubercles, almost abortive. (Plate 

 63, fig. 2). 



The setae are mostly compound. The shafts of these are slender, with the 



