ASTEEOIDEA 631 



P. militaris (0. F. Muller) (Fig. 979). Arms short and thick; disc 

 thick and arched ; under side flat ; diameter 9 cm. : circumpolar, south to 

 Cape Cod and Washington, in 10 to 350 fathoms; 

 Europe. 



ORDER 3. FORCIPULATA. 



Pedicellariae pedunculate, with either crossed 

 or straight jaws; spines conspicuous; aboral skele- 

 ton reticular: 7 families. 



Key to the families of Forcipulata here de- 

 scribed: (Leunis). 



c x Arms not sharply set off from the central disc. 



&! Aboral skeletal plates almost contiguous 1. STICHASTEBIDAE 



6 3 Aboral skeletal plates from a reticulum 2. ASTEBIIDAE 



o a Arms sharply set off from central disc 3. BEISINGIDAE 



FAMILY 1. STICHASTERIDAE. 



Starfishes with long, slender arms; aboral plates large and in longi- 

 tudinal rows ; 4 rows of feet : 4 or 5 genera. 



STICHASTER Muller and Troschel. Numerous spines on each side 

 of the ambulacral grooves: 10 species. 



A. albulus (Stimpson). Diameter of disc 2 to 3 cm.; 6 cylindrical 

 rays, usually in 2 groups, 3 long and 3 short ones: Cape Hatteras (deep 

 water), to the Arctic Ocean, low-water mark to 200 fathoms; often 

 common. 



FAMILY 2. ASTEEIIDAE. 



Starfishes with usually a small disc and 5 to 12 or more arms; 

 aboral plates with a reticulate arrangement and bearing spines; pedicel- 

 lariae with straight and crossed jaws; 4 rows of feet: about 10 genera. 



ASTERIAS L.* Usually 5 arms present; 1 or more rows of movable 

 spines on each side of the ambulacral groove; pedicellariae with crossed 

 jaws around the base of the spines and with straight jaws among the 

 papulae: numerous species; in shallow water in most seas, being com- 

 monest in temperate zones, and especially abundant and reaching very 

 large size on the North Pacific coast of America. 



A. forbesi (Desor) (A. arenicola Stimpson; Asteracanthion bery- 

 linus A. Agassiz). Common star (Fig. 980). Rays stout and tending to be 

 blunt and cylindrical; spines rather few and coarse; madreporite bright 

 orange; color very variable, being oftenest greenish-black; diameter 16 



* See "Natural History of the Starfish," by A. D. Mead, Bull. U. S. Fish. Com. 

 for 1899, p. 203, 1900. 



