ASTEBOIDEA OF NORTH PACIFIC AND ADJACENT WATERS — FISHER. 27 



conspicuous and three underlie the terminal plate. All these "plates" are invisible 

 until specimen is dry. Between the flaring outer ends of companion mouth plates 

 is a triangular unj)aircd plate, the exposed portion of the primary oral plate or 

 odontophore. 



Madreporic body large, adjacent to a median cribriform organ. Tt is about as 

 wide as the latter. Striations deep and radiating. 



Color in life: general tint whitish; bluish cast on disk due to viscera showing 

 through integument. 



Anatomical notes. — Superambulacral plates absent. Peristome contains small 

 irregular perforated rods and plates especially on the lips. There are also a few 

 simple straight and curved rods. Tube feet large, conical, without calcareous 

 particles in walls. Ampulhe single, not double. The stomach is very simple, 

 possessing very short radial pockets. The dorsal wall is closel}' bound to the 

 abactinal body wall. There is no intestine and no anus, nor any sign of an intes- 

 tinal ccEcum. A prolongation of the ccelom fills the so-called "epiproctal" cone or 

 dorsal peduncle, but the opening into the peduncle is closed bj^ a layer of muscles. 

 Gonads small, one on each side of the interradial septum. 



Variations. — The specimens from California, six in number, j)resent very few 

 variations of importance. There is some difference in the width of the abactinal 

 area on rays as explained above. Superomarginals range from fifteen to eighteen 

 and there may be one to three superomarginal spines. There is sometimes but one 

 adambulacral spmelet although there are usually two. The segmental papilla can 

 be recognized as such on as many as fifteen adambulacral plates, and varies all the 

 way to only five. It gradually is transformed into a lanceolate spinelet so that it 

 is not easy to limit exactly the number. 



Numerous smaller specimens from Albatross station 2859 vary more widely. 

 R averages about 22 mm. and r S mm. (R = 2.75 r). But one specimen hasR = 22 

 mm., r = 6 mm., R = 3.6 r, wliich is fully as long a ray as in the tj-pe. Superomar- 

 ginal plates twelve to seventeen. Out of forty-five specimens from this station 

 thirty-three lack entirelj' tiie superomarginal spinules, five have a spinelet here and 

 there along the superomarginal series, and seven have a regidar series of supero- 

 marginal spinules. These are lacking usuallj^ from the first two plates, and may be 

 absent from an odd plate here and there. The marginal plates are a trifle smaller 

 and weaker than in Californian examples. There is usually but one true furrow 

 si)inelet, which is curved antl compressed. Rarely two are ])resent, the second 

 being placed directl.y behind the first. Segmental papillte can be recognized as such 

 for about one-half to three-fourths the length of furrow although tlie rudimentary 

 pit is present only on the first four or five plates. The terminal plate has three 

 instead of five spinelets. 



The most important difference between these specimens and the Californian 

 examples is the absence of superomarginal spinules in many of the former. Their 

 presence in almost typical form iij seven specimens shows however that supero- 

 marginal spinules are not wholly trustworthy as a specific character. The tiifference 

 in the number of adambulacral spinelets is variable even in Californian examples. 

 The diflference in size may account for the more frequent presence of two spinelets 

 in largest examples. The so-called "segmental jiaiulhc" of the ailanibulacral 



