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BULLETIN 76, UNITED STATES NATIONAL MUSEUM 



numerous tabulated branches, irregularly arranged. The opening appears to be on 

 the side of the ray, close to the interradial angle on a level with the superomarginal 

 plates, which here bend upward. No Polian vesicles observed. Ampullae single, 

 large, crowded. 



Young. — Numerous young specimens taken alone and with adults, the smallest 

 having R 9 mm., differ in appearanco chiefly on account of the fewer dorsolateral 

 spines and the relatively smaller intervals of the skeleton. The numerous connecting 

 secondary ossicles of the adult are much fewer in number. The crossed pedicellariae 

 are absolutely diagnostic in cases of doubt. On Plate 44, Figures 2, 3, 4, various 

 details of the skeleton of immature examples are shown. Only a few of the secondary 

 carinal and superomarginal ossicles are developed; the interbrachial "septum" or 

 buttress has fewer plates than in the adult; only the first pair of adambulacrals meet 

 behind the mouth plates; there are no actinal plates, the apparent first actinals being 

 in reality the first superomarginals displaced. In examples with R less than 20 mm. 

 ambulacral pores are in two series. 



A specimen with R 20 to 25 mm. is easily identified. It has three dorsal lines of 

 spines, unequal furrow spines, bare actinal interradial areas, and characteristic 

 pedicellariae. In young specimens both the first and second pair of adoral adambulac- 

 rals at first have two spines each. Later the first plate loses the subambulacral and 

 sometimes one of the second pair also loses a spine, leaving a transverse series of three 

 for the pair. In specimens with R 50 to 100 mm. the straight dermal pedicellariae 

 are disproportionately big, being nearly as long as the dorsal spines and considerably 

 thicker when their "sheath" is still covering them. 



Orthasterias leptolena is the young phase of forreri. 



Type-locality. — Off Santa Cruz, Monterey Bay, Calif, (de Loriol). 



Distribution. — Southern Alaska to San Diego, Calif.; 16 to 291 fathoms, on 

 rocky bottom; temperature range, 43° to 51.8° F. 



Specimens examined. — Eighty- three. 



Specimens of Slylastcrias forreri examined 



