ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS — FISHER 143 



sivo and strongly united to the fivo heavy calcified interbrachial septa. On either 

 side of the adoral end of the adambulaeral ridge, (composed of the first two united 

 ambulacra) ossicles) is a large pore corresponding to the first tube-foot. The suc- 

 ceeding three pores form a triangle just back of this adoral knob, the length of which 

 equals that of the next six plates. Ampullae single, in a close double series on either 

 side. 



Young. — Two very small specimens were taken at station 4431 along with a big 

 specimen, and with the adults and peculiar young of Sclerasterias heteropaes. One 

 specimen measures R 3.5 mm.; the other R 8 mm. The latter greatly resembles a 

 Sclerasterias as it lacks actinal plates and has "beaded" areas on the superomarginal 

 plates. However, unlike Sclerasterias of this small size, the crossed pedicellariae are 

 in wreaths surrounding the base of the carinal and 9uperomargina] spines (no dorso- 

 lateral spines) and form a tuft on- the outer side of the outer inferomarginal spine. 

 Here and there the forerunner of another tuft has appeared on the inner spine — 

 which is never the case in Sclerasterias. The form of the crossed pedicellariae is also 

 characteristic. There are about 12 superomarginal plates with relatively coarse 

 spines on the alternates. This arrangement, the beaded areas, and the absence of 

 dorsolateral spines on the pentagonal ray gives the appearance of ,SY/, rash ri.as. 



An example from station 3159 with R 22 mm. is figured. (PI. 47, fig. 4.) There 

 are five to eight actinal spines, varying on the 10 areas, while the dorsolateral spin, b 

 are confined to the distal part of ray. The straight pedicellariae are few and com- 

 pressed lanceolate. The relatively stout spines are slightly grooved at the end. 



Variations. — The most conspicuous variations are in the numbers of major 

 pedicellariae, the form and stoutness of the abactinal spines, the occurrence of supero- 

 marginal spines, whether on alternate or consecutive plates, and the degree of regu- 

 larity or rather irregularity of the carinal and dorsolateral plates. 



The carinal spines form a slightly wavy line in typical specimens, but in extreme 

 cases, as at station 4233, 39 to 45 fathoms, Yes Bay (forma leptostyla), it is impossible 

 to follow the carinal series with certainty, and even the superomarginal series is 

 irregular. 



The spines seem to thicken and to become terminally scored with increasing age; 

 but at the same time, irrespective of age, the spines become slenderer in depths of 

 30 fathoms or more, and tend to lose the terminal furrows. 



In the specimen from station 4202, used in the description, the spines are about 

 a mean between the stoutest and slenderest. The longest are about 5 mm., by 1 

 nun. at base, and the tip is slightly swollen, obtuse, and furrowed anywhere from four 

 to ten times, the grooves being shallow. 



The irregularity in occurrence of the superomarginal spines, whether on all 

 plates or only on alternates, is apparently not correlated with geography or depth. 

 On the outer part of the ray the spines arc almost always on every plate, but proxi- 

 nially, there is great variation, differences occurring on different rays of the same 

 specimen. 



The spines are on most of the proximal, as well as distal plates in specimens 

 from stations 4431 (southern California), 4555 (Monterey Bay), 3443 and 3445 

 (Straits of Fuca), 423:: (Yes Bay, Alaska); and Monterey Bay, lowest tide (some 

 specimens). They prettj generally are on alternate plates proximally in examples 



