70 



BULLETIN 76, UNITED STATES NATIONAL MUSEUM. 



lacral plates will serve to distinguish tiiis species from californicus, especially when 

 other characters fail. Gonads arranged in a tuft on either side of the intcrradial 

 line. SLx Polian vesicles present, one in each interradius except that of madre- 

 poric canal, in which there are two; the same interradius having a double inter- 

 ratlial sejitum, the others a single. Two Tiedemann glands to each interradius. 



Color in alcohol, bleached yellowish to whitish; color in life unknown. 



Varkitions. — The variations in this species mostly concern minor details of 

 ornamentation — characters which are unstable in nearly all species of starfishes. 

 Tims the spinelets are fewer in small specimens and are slightly more robust in 

 some than in others. As usual the smaller specimens have shorter, stouter arms. 

 There are a relativeh- few specimens of A. californicus (stations 3145, 3147, 3148, 

 3172) which bear a certain resemblance to ornatissimus, chiefly because the paxillis 

 are larger and more uniform, as seen superficially, than in typical examples. The 

 paxillar spines, however, are shorter and more compact and the auxiliary infero- 

 marginals spines (that is, the lateral ones) are short, while the comb of teeth on 

 tiie ambulacral plates, described above, is entirely lacking. Likewise the enlarged 

 adambulacral spinelet is of character of californicus — much flattened, relatively 

 short with a round tip, and not very conspicuously tapered. It is barely possible 

 that some of these aberrant examples of californicus may be hybrids. There is 

 no good evidence that the two species intergrade, although it is not impossible or 

 even improbable that they may converge somewhere off Lower California. The 

 forms, though different, are so similar in genei'al structure that one is impressed 

 with the notion that they may be offshoots of a common species still livmg in the 

 south, possibly A. veniUi or a nearly related form. There is a wide difference, 

 though, in the toothed and smooth upper edge of the ambulacral plates. 



Youn^. — In small specimens of ornatissimus the characters of the adult are 

 fairly obvious, especiaUy when examples are compared with equal-sized individuals 

 of californicus. The paxfllce are large and the superomarginal plates encroach 

 onto the abactinal area rather more than in the adult. In a specimen with R equal 

 to 20 ram. (r = 6.5 mm.; R = 3r) there are about three transverse rows of abactmal 

 paxillae opposite every two superomarginals at base of ray, and about ten paxUlje 

 to a transverse row, opposite the second superomarginal. Superomarginal plates, 

 twenty; lateral spmes of inferomarginals, two or tlu-ee, the auxiliary lateral spines 

 well developed and actinal inferomarginal spinules prominent. Adambulacral 

 armature similar to that of adult, the long spine of second series (first actinal) well 

 developed. Usually there are only two actinal series each with two spines, the 

 outer shorter than those of furrow series. 



Changes in dimensions due to size are showTi in the following table: 

 Table showing variations in Astropecten ornatissimus. 



