ASTEROEDEA OF NORTH PACIFIC AND ADJACENT WATERS — FISHER 61 



plentifully on the marginal plates, and sparingly on the actinal area. The larger 

 kind have slenderer jaws with two pairs of prominent terminal teeth and on the 

 inside of each jaw two, less often three, slender sharp thorns. The largest measured, 

 from a huge specimen, was 0.6 mm. long, but this is exceptional; 0.45 to 0.55 mm. 

 is the average largest on big specimens. Small examples have the same sort, only 

 smaller — about 0.28 to 0.3 mm. in an example with R 12 mm. (See pi. 27, fig. 2b, 

 magnified 200 times, twice that of the figures 2, 2a. PI. 26, figs. 1, la, lb, lc, are 

 from very small typicus, enlarged x200; lc is abactinal.) The smaller pedicellariae 

 (pi. 26, fig. 2f) are much shorter and relatively broader, with a broad, many-toothed 

 terminal portion, similar to that of the usual type of small crossed pedicellaria. 



Both kinds differ from the corresponding ones of true typicus (of which a specimen, 

 probably from Norway, was loaned by Dr. H. L. Clark). Compare Plate 26, Figures 

 1-1 b, showing the larger pedicellariae of typicus magnified 200 times, with Plate 27, 

 Figure 26, showing those of a small specimen of magister from station 4792, same 

 enlargement. Figures 2 and 2a are enlarged only 100 times. The jaws of the pedi- 

 cellariae from typicus are much heavier and have four to six median teeth. The 

 smaller sort (pi. 26, fig. lc), distinguishable by the many toothed terminal margin, 

 is also different, having more numerous teeth on the cutting edge of the jaw, as well 

 as a somewhat different form. 



The straight pedicellariae are absent in some specimens; in others a very few tiny 

 ovate ones, sometimes blunter than the figure, occur sporadically along the margin 

 of furrow and at the base of the innermost oral spine — in the last position, always 

 singly. (Length, 0.25 to 0.27 mm.) 



Madreporic body inconspicuous, often irregular, one-third to one-fourth distance 

 from margin to center. 



Young specimens. — These have slender rays and the skeleton is characterized by 

 a restriction of the dorsolateral plates to one or two series, while the actinals are 

 in one or two longitudinal series (one series in a specimen with R 12 mm.). It is 

 curious that these very small specimens do not show the arrangement in transverse 

 series which is so characteristic of mature individuals. A specimen from station 

 4243 with R 28 mm. does not exhibit any multiplication of the distal actinal plates 

 (one longiseries beyond middle of ray). However, another from station 4792, with 

 R 30 mm., has four or five actinal plates in each transverse series and is constructed 

 like one of the very large examples. One of the generic characters, therefore, is not 

 found in very small specimens and may not appear until R is about 30 mm. In 

 lieu of the actinal plates, the terminal claws of the crossed pedicellariae will suffice to 

 distinguish young Pedicellaster from young Anteliaster. 



It is noticeable that the plates of the young have stout lobes like those of the 

 adult. The immature stage can be readily separated from those of megalabis on 

 plate as well as pedicellarian characters. 



The spinelets are relatively slenderer than in the big specimens with R 60 to 85 

 mm.; there is usually one to a plate, and the pedicellariae are less crowded. 



Anatomical notes. — The gonads form each a bush}^ tuft of branched tubules and 

 open 3 to 5 mm. from the interbrachial angle (R 70 mm.), on the side of the ray in a 

 variable relation to the plates — sometimes between the inferomarginal and actinal 

 plates, and in one case just above the superomarginal series. 

 64406— 28— -5 



