NO. 3 HARTMAN : POLYCHAETOUS ANNELIDS 335 



thorax includes 4 parathoracic segments; the opercular crown has an 

 outer series of about 18 pairs of spines, the inner row consists of only 4 

 pairs. There is a single pair of dark nuchal hooks on the dorsal side; each 

 is strongly falcate, with a broad base and sharp cutting edge, much as in 

 Lygdamis asteriformis (above). The outer paleae are pale, somewhat 

 flattened, taper distally. The inner row is limited to 2, 3, or 4 pairs of 

 shorter, darker, tapering, blunt spines, about as thick as the outer ones, 

 but distally blunt. 



The oral tentacles are long, consist of about 12 rows on a side, but 

 there are few in a row. Palpi are well developed, long, cylindrical. The 

 first parathoracic paleal-bearing segment is notably smaller than the 3 

 following, but similar in other respects. It is herewith referred to the 

 genus Lygdamis. 



Alonorchos Treadwell (1926, p. 190) was newly erected for this 

 single species, supposedly differing from other genera in that a single 

 row of paleae was thought to be present, but a second row is actually 

 described and originally figured. A reduced number is characteristic for 

 this species, as in some others of the genus Lygdamis (see L. asteriformis, 

 above). It seems unnecessary to erect a genus for the reception of this 

 species. 



Distribution. — L. philippinensis has remained unrecorded save through 

 its original discovery, from the Philippines, in 805 fms. 



Genus IDANTH YRSUS Kinberg 

 Type I. armatus Kinberg 



(Includes Pallasia Quatrefages, preoccupied in Diptera and Pisces, 

 see Johansson, 1927, p. 87.) 



Idanthyrsus differs from Lygdamis (above) mainly in having only 3, 

 instead of 4, paleal-bearing, parathoracic segments. The operculum has 2 

 rows of modified spines. There are 2, to a few, heavy nuchal hooks on the 

 dorsal side of the operculum. Oral tentacles are developed. 



Two species, /. pennatiis and /. armatus (below), have been widely 

 reported, especially from shallow seas. As already shown (Augener, 1914, 

 pp. 79-82, and others) /. armatus is veiy close to the older /. pennatus 

 and may be only a variety. Another closely related species, /. ornamen- 

 tatus (below), is here recognized, although its affinities with the others 

 are obvious. In addition, a sabellarian was described by Bosc (1802) 

 from Charleston Bay, S.C, as "Sabella negata," later referred to Pallasia 

 (Quatrefages, 1848, p. 25) without enhancing the original brief account, 

 but it remains too incompletely known to be determinable. 



