IDANTHYRSUS REGALIS. 4S7 



gradually distad into a conspicuous entire blade which is distally unsymmetrical , 

 one distal edge being more oblique, the tip narrowing to an acute point which 

 is curved to one side; the blade is also moderately curved distally, at right 

 angles to the flat surface. (Plate 75, fig. 13, 14). In addition, there are in each 

 paleae-bearing notopodium, a few stout setae not flattened, and narrowing uni- 

 formly to an acute tip. (Plate 75, fig. 9) . The ventral thoracic paleae are much 

 more slender, with the shafts more uniform and widening more abruptly into a 

 distal, sublanceolate, and usually symmetrical blade, which is also somewhat 

 curved at right angles to the broad surface. (Plate 75, fig. 15). The abdominal 

 segments bear notopodial setae that are long and fine, forming small fascicles. 

 (Plate 75, fig. 8). The uncini are small and slender, with usually seven teeth. 

 (Plate 75, fig. 10). 



Locality. Near Panama: Taboguilla Island. In coral, 1 fm. below 

 low tide-mark. 31 October, 1904. One specimen. 



This species also belongs in the group to which /. johnstoni (Mcintosh) 

 pertains. It is very close to /. armatus Kinberg described originally from 

 near Valparaiso, Chile, and known as common in the region of the Magellan 

 Strait, wliich seems to be its center of distribution. Kinberg's description is insuf- 

 ficient, but Ehlers regards liis Pallasia sexungula (and also Hermella macropalea 

 Schmarda) as the same species, and comparisons may be made with his descrip- 

 tion and figures. The present species seems to be broader across the opercular 

 lobes, these diverging more widely. The nuchal hooks, of which but one pair 

 is present in place of the three pairs usual in armala, though this is possibly 

 not so significant as was formerly thought, are very much stouter. The inner 

 paleae are, relatively to the outer ones, much shorter. Ehlers's figm'e represents 

 (Nach. K. gesellsch. wiss. Gottingen. Math. phys. klasse, 1897, pi. 12, f. 194) 

 on the second setigerous somite four small, contiguous, cirriform processes 

 between setae and the large dorsal cirrus, or branchia, whereas in the present 

 species there are but two, these being relatively clearly longer and being widely 

 separated. The mouth in cretus is broader anteriorly and the lateral folds are 

 stouter and more widely separated. 



Idanthyrsus REGALIS, sp. nov. 



Plate 74, fig. 1-8. 



The head and gills are purplish brown, excepting for a longitudinal light 

 area below the caudal half of the outer opercular ridge and a broad encircling 



