26 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



than distally, perfectly smooth, and distinctly separated from each other. The IBr 2 

 (auxiliaries) are much broader than long, smooth, with the lateral edges very short 

 and the distal edges slightly concave. 



The 10 arms are 17 to 19 mm. long. The first brachials are broader than long with 

 the outer edge somewhat longer than the inner, the inner edges of adjacent first 

 brachials touching each other, at least proximally. The second brachials are similar, 

 but the distal margin is not so straight. The first sj T zygial pair (composed of brachials 

 3+4) is about as long as broad, with the two component elements equal and discoidal. 

 The brachials following are more or less oblong, with the outer and inner sides usually 

 differing slightly in length. All the brachials are smooth and rounded dorsally, and not 

 only do they not overlap, but they are scarcely in contact except at the syzygies. 



Syzygies occur between brachials 3+4, 7 + 8, and 11 + 12 (rarely 10+11), and dis- 

 tally at intervals of 2 (or more commonly one) muscular articulations. 



The pinnules are rather few, from 12 to 15 on each side of an arm, and are widely 

 spaced owing to the length of the brachials and the frequent syzygies. 



P t is stout, 2.3 mm. long, and is composed of 7 smooth and semicylindrical seg- 

 ments. The first two segments are about as broad as long, the third, fourth, and fifth 

 are longer than broad, and the terminal segment is minute and blunt. 



P 2 is very short, about 1 mm. long, with only 4 segments. The pinnules succeeding 

 are less stout and are composed of 8 to 14 segments of which the basal ones are large, 

 but only a little expanded laterally. 



Sacculi are abundant and large, expecially on the distal pinnules, but there are 

 very few on the disk. When dry, the disk shows many small calcareous plates, largest 

 and most conspicuous beside the ambulacral furrows and around the base of the anal 

 tube, which is about as long as half the diameter of the disk or longer. The oral surface 

 of the arms and pinnules seems to be free from plates. 



The color of the skeleton is very light brown, that of the soft parts and sacculi very 

 dark brown. In the terminal half of the cirri more or fewer of the segments are dorsally 

 marked, or strongly tinged, with purple. 



This description was based upon 23 specimens from off Manning river, New South 

 Wales. 



Remarks. Dr. H. L. Clark said that he placed this interesting species in the genus 

 Himerometra only after considerable hesitation, on account of its small size, the ab- 

 sence of any swelling or convexity of the IBr series, and the very small number of 

 cirri. He noted that it resembles Oligometra in many respects, but the large number 

 of cirrus segments distinguishes it from the species of that genus. It seemed to him 

 better to include it in the large and somewhat heterogeneous group Himerometra (in 

 the sense in which it was understood in 1909) rather than to modify the definition of 

 a smaller, natural group like Oligometra. 



He remarked it might be thought that we have here simply a young form of 

 Ptilometra, especially as these specimens occur only with the adults of that genus. 

 Fortunately, however, there are young specimens of Ptilometra (mulleri) in the collec- 

 tion as small as the larger specimens of paedophora, and it is possible, therefore, to 

 show that the two are not even nearly allied forms. The conical centrodorsal, the 

 long cirri, and the crowded prismatic pinnules distinguish the Ptilometras at a glance. 

 Moreover, it should be noted that pentacrinoid larvae were not present on the pin- 

 nules of any undoubted Ptilometra mulleri, even among those from Thetis station 28. 



