ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS — FISHER 137 



two series of superornarginals. The inferomarginul spines are unusually deeply 

 gouge-shaped and variously eroded or sculptured by irregular channels. * (PI. 61, 

 figs, le.) A similar, though less striking, variation toward multiple superomargiiial 

 spines is shown by the specimen of nanimensis from station 3464. 



Anatomical notes. — In the cleaned skeleton the carina! plates are clearly distin- 

 guishable from the others as they imbricate strongly, whilst the dorsolaterals are 

 generally connected by slender secondary ossicles. The carinals have four short 

 lobes while the dorsolaterals are usually irregularly three or four lobed, or elliptical. 

 (PI. 61, fig. 1.) The smaller, secondary ossicles often carry spines. The dorso- 

 lateral plates are very irregularly arranged, there being no semblance of series at 

 the base of the ray, but on the outer attenuate part, three or four series can be distin- 

 guished on either side of the carinals. The superomargiiial plates are the largest of 

 all, are strongly four-lobed, the transverse lobes being the more prominent, while the 

 strong descending lobe is the longest. The plates are not, however, very large when 

 compared to those of Marthasterias or Sclerasterias in which the intermarginal area 

 is broad, especially in species of the latter genus. On the outer half of the ray the 

 plates of the two marginal series are more nearly of a size. The ventral lobe of the 

 inferomarginals is shorter than the dorsal and longitudinal lobes. Between the 

 inferomarginal and adambulacral plates is a single series of small oblong-elliptical 

 actinal plates placed one opposite each inferomarginal, with the ond toward the surface 

 and superficially hidden by tissue. The series extends nearly to the end of the ray, 

 but the distal plates are very tiny. The ambulacral ossicles are somewhat larger 

 than those of Orthasterias Icoehleri and more crowded than in Stylasterias fonrri. 

 It is not easy to give comparative measurements of these plates because there is no 

 constant for comparison. In the large Port Chester specimen of Stylasterias jornri 

 there are 10 ambulacral plates in a space of 10 mm. at the base of the ray, while in 

 a comparable example of chelifera from station 4787 there are 13, and in Orthasterias 

 Icoehleri of the same size, 15 or 16. The pore scars are oval or pyriform, as in Stylas- 

 terias, but narrower. 



The actinostomial ring is stout (pi. 62, figs. 1, la) and the actinostome broader 

 than is Stylasterias. The proximal end of the ambulacral ridge is as long as the se\ en 

 succeeding plates. The first ampulla pore is scarcely larger than the following three 

 (which form a triangular group) while in Stylasterias the following three or four are 

 much smaller. The interbrachial septa are strongly calcified but are small on account 

 of the small size of disk. The odontophore has two pits where it abuts against the 

 interbrachial septum. 



A comparison of the skeleton with that of Orthasterias Icoehleri shows a very strik- 

 ing similarity in form, spinulation, and mode of connection of the abactmal and mar- 

 ginal plates, and in the relative size of the ambulacral ossicles. There are two points 

 of difference: The actinal plates of Orthasterias IcoeUeri are larger, bear a spine at the 

 lower end, and the proximal plates, at least are im-ipicntly four lobed. These lobes 

 are entirely covered by the inferomarginal plates, only the ventral end of the aninal 

 plate being visible externally. The second important difference is the narrow oral 

 angle of Orthasterias, composed of small mouth plates plus five pairs of contiguous 

 adoral adambulacral plates, as against two in chdifera. The mouth plates of chdijera 

 are about twice as broad as those of Orthasterias. 



Viscera.— The intestinal coccum has three long divisions which are irregularly 

 subdivided and lobed, the longest subdivision being about as long as the diam< 



