36 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 7 



Elytra 18 pairs, the first pair orbicular (pi. 4, figs. 43, 45), the 

 others transversely oval (pi, 4, fig. 44). The first pair (and sometimes 

 also the second) have two kinds of macrotubercles, (1) a translucent 

 yellowish, slightly hooked, with terminal knobs, and (2) conical, white 

 or opaque mound, lacking a stalk, ornamented with shallow convolu- 

 tions (pi. 4, fig. 46). In addition, there are great numbers of micro- 

 tubercles scattered more or less regularly over the surface. The area 

 over the elytral scar is pale, with an irregular dusky ring surrounding it. 

 More posterior elytra are smooth, except for a few microtubercles along 

 the anterior margin, near the concavity (pi. 4, fig. 50). The surface is 

 underlain with a fine reticulated mesh, that is darkest and coarsest in 

 an area around the elytral scar. An area over the hilum is pale (pi. 4, 

 fig. 44). 



Parapodia are robust, fleshy; on median segments the cirrophores 

 are about as heavy, and nearly as long, as the stout neuropodia. The 

 notopodia are reduced, but with a projecting aciculum and a fascicle 

 of fine setae. The dorsal cirrus is slender, tapering, with a slight sub- 

 terminal thickened area and a dusky ring; it extends distally about as 

 far as the neuropodial setae. Ventral cirrus is pale, short, tapers rapidly 

 from a stout base and terminates in a slender prolongation not reaching 

 to the end of the neuropodium. 



Notopodial and neuropodial setae are each of one kind though of 

 different sizes. There are 10 to 15 notopodial setae in a fascicle, in- 

 cluding superior shorter (pi. 4, fig. 47) and longer, slenderer setae 

 (pi. 4, fig. 49). The neuropodial setae are much coarser, longer, and 

 include 12 to 15 in a supraacicular fascicle and 18 to 24 in a subacicular 

 fascicle; the two fascicles form a continuous series of 3 or 4 vertical 

 rows. They are bifid distally (pi. 4, fig. 48). 



Halosydna elegans Kinberg (1857, p. 18) from the Galapagos Is- 

 lands was described without elytral fringe. Later, Monro (1928a, p. 

 567) reported it from the Galapagos Islands, and added to the original 

 meagre description. H. glabra differs from H. elegans particularly in 

 having a greatly reduced notopodium, also the larger elytral tubercles 

 are convoluted and do not have a flat top. 



Holotype. — AHF no. 4. 



Distribution. — Concepcion Bay, Gulf of California, Mexico; Piiias 

 Bay, Panama. In coral and coralline zones, to 12 fms. 



