12 NATURAL HISTOEY BULLETIN 



Order Forcipulosa Verrill or Forcipulata Perrier. 



Stelleridw forcipulatce Perrier, Mem. Etoiles de Mer, pp. 166, 188, 1876. 



Forcipulata Perrier, Exped. Sci. Trav. et Talisman, p. 27, 1894. 



Asteries Amhulacraires Viguiee, Squellette des Stellerides, Arch. Zool. 



Exper., VII, p. 93, 1878. 

 Cryptozonia (pars) Sladec, Yoj. ChalL, xxx, pp. xxxiv, 397,, 1889. 

 Adetopneusia (pars) Sladen and Leptostroteria (pars), op. cit., p. xxxiv. 

 Forcipulosa Verrill, op. cit., p. 24, 1914a. 



In this order the form is always stellate, often with long rays, 

 commonly five, but often multiple. Ambulacral plates, except 

 the orals, are usually short and closely crowded (leptostroterial) ^ 

 but not in Brisingidw. The proximal pair is elongated and, ex- 

 cept in Pedicellaster and a few others, forms the inner end of the 

 jaw. Ambulacral feet are generally arranged in four rows; 

 but in two rows in Pedicellasteridm, BrisingidcB, and Zoroaster- 

 idcB. In certain large species of Pisaster there may be more than 

 four rows. 



Aside from the ambulacral and adambulacral plates, the skel- 

 eton of the rays consists of five fundamental or primary rows of 

 ossicles, viz., the median dorsal or carinal; the two superomar- 

 ginals; and the two inferomarginals. The latter may or may 

 not be confined to the ventral side. 



The ossicles of adjacent rows may be articulated directly by 

 their lobes, or small, simple connecting ossicles may intervene. 



This simple or primitive type of skeleton is found in Cor- 

 onaster hriareus (see pi. ix, fig. 4) and some other genera, espe- 

 cially when young. 



In most cases more or less numerous ossicles or rows of ossicles 

 are interpolated during growth between the five primary rows, 

 either above or below, or between the marginals, thus giving rise 

 to m^any different styles of skeleton in the more complex genera. 



The carinal or median dorsal plates usually remain distinct, 

 but are often small and not easily recognizable. The two mar- 

 ginal rows are nearly always easily recognizable, though small, 

 and they generally bear spines larger than the dorsals. They 

 never form a stout margin, as they do in the Paxillosa. 



Interactinal plates are various. Usually there is at least one 

 row, the peractinals, but these are often small and spineless and 

 sometimes are lacking. In other genera there may be several 

 rows of spiniferous interactinals. 



