252 PROCEEDINGS OF THE ACADEMY OP [April, 



but not longer, those of the anterior branchial region being ten to 

 twelve times as wide as long, decidedly depressed and equally convex 

 dorsally and ventrally. The smaller specimen is widest at about the 

 posterior end of the anterior fourth and tapers thence caudad. Caudal 

 end and pygidium unknown. 



Parapodia begin on II at a low level and gradually rise to about XV, 

 where they occupy about a middle level. First four small, the others 

 of normal proportions and differing in no essential from those of M . 

 stylobranchiata, although the postsetal lobe is relatively broader (that 

 of IV is abnormally bifid). 



Gills when fully developed pectinate, consisting of a short basal 

 stem bearing from four to six slender, tapering, cross-wrinkled, crowded 

 filaments not exceeding a length of one-fifth of the body width and 

 none of which reaches the median line. On the type they begin at 

 XXXIII on the left side with two filaments and at XXXIV on the 

 right side with two filaments; three filaments occur on each side of 

 XXXVI; for the next fifteen segments four is the usual number of 

 filaments; between LV and LXV five is more frequent and thence to 

 LXXXV or LXXXVI the maximum number of five or six or rarely 

 even seven occurs ; behind this to the end of the piece all gills are quin- 

 quefid. On the smaller specimen the gills begin farther forward and 

 are much simpler. From XX or XXI to XXV they are simple, to 

 XLIV and LI bifid, thence to about XC mostly trifid, then again bifid 

 to CXXIV, and after that to the end of the piece they consist of a single 

 filament. 



Neuropodial acicula are simple, straight, tapered, blunt-pointed 

 spikes, black or nearly black to the tips. On anterior parapodia there 

 are four to six, with the tips little or not at all exposed and arranged 

 in an oblique series between the two tufts of setse. Farther back 

 on middle segments there are only three much stouter acicula, the 

 nearly black tips of which are conspicuously exposed. The cotype 

 has only two of the spinelike acicula on middle parapodia and in 

 addition a pale, more slender, bifid and hooded ventral crochet (PI. 

 VII, fig. 16), which is missing in all of the preparations made from the 

 type. 



Setse generally more prolonged than those of M. stylobranchiata. 

 Post-supra-acicular tuft very dense on anterior segments, consisting 

 of numerous curved, tapering alimbate setse (PI. VII, fig. 13), the 

 dorsal ones longer, more slender and colorless, the ventral shorter, 

 stouter and yellow. On these segments the pectinate setae are few 

 and difficult to see and bear numerous fine teeth (PI. VII, fig. 14a). 



