IDANTHYRSUS REGALIS. 489 



The next succeeding thi-ee somites are longer. Each bears below a neuro- 

 podial fold from which springs a series of paleae of moderate size. Above this 

 is the prominent notopodial ridge which bears a series of larger paleae. Above 

 the notopodial ridge on each side is a basally stout, conical, dorsal cirrus or 

 branchia. 



The dorsum of the abdomen is flattened or somewhat concave. The ventral 

 surface is grooved, the long neuropodial setae projecting over it and those from 

 the opposite sides overlapping. Behind the setigerous process the nem-opodium 

 extends into an acutely pointed, postsetal hp. On the anterior and median 

 somites the uncinigerous ridges, or tori, extend from the dorsal cirri or branchiae 

 to the neuropodia. In the type cirri are present on somites to the twenty fourth, 

 inclusive. They are longest near the middle of abdominal series. Each is 

 gradually attenuated and conically pointed, those of the thorax being relatively 

 much stouter than the following ones. 



The inner opercular paleae are dark in color and smooth. The distal ends 

 are acutely acuminate and curved mesad. (Plate 74, fig. 6). The outer paleae, 

 excepting the most anterior, have the shafts distally acuminate, the acvuninate 

 portion long. Numerous rather long processes fringe each side. (Plate 74, fig. 7) . 

 At the anterior end the shafts are stouter and conspicuously clavate, with along 

 each edge in place of the long, filiform processes, a series of .shorter serrations. 

 (Plate 74, fig. 8). 



An ordinary neuropodial seta of the thorax is shown in Plate 74, fig. 1. 

 The notopodial paleae of the last three thoracic somites are broad and flat, 

 slightly and gradually enlarging from the base to the distal end, which is rather 

 abruptly narrowed to a slender acute tip. (Plate 74, fig. 5). The neuropodial 

 paleae of these somites are somewhat similar in form to the notopodials, but are 

 smaller and more gradually attenuated distad. (Plate 74, fig. 4). The neuro- 

 podial setae of the abdominal somites are unusually long. They are of the 

 usual general structure. (Plate 74, fig. 2). The uncini have the body slender. 

 Typically each bears eight long, slender teeth, of wliich the longest are at the 

 middle of the series and the smallest next to the inferior end. (Plate 74, fig. 3). 



Locality. Galapagos Islands: Chatham Island. 9 January, 1905. One 

 specimen. 



This species has anteriorly the violet-brown pigmentation that is so charac- 

 teristic of Pallasia pennata Peters {Hermella bicornis Schmarda, Pallasia sex- 

 hamata Grube, Sabellaria australiensis Haswell, and Pallasia porrecta Ehlers); 

 but to the naked eyes it appears strikingly different because of the large opercu- 

 lar lobes and their great divergence from each other, the diameter across the 



