626 ECHINODERMATA 



Order 1. PHANEROZONIA. 



Either 1 or 2 rows of large marginal plates along the sides of the 

 arms (Fig. 971), these plates being in contact with one another and 

 giving the arm a definite margin; 2 rows of ambulacral feet in each armj 

 pedicellariae often wanting, and when present, sessile : 8 families. 



Key to the families of Plianerozonia here described : 

 tti Aboral wall membranous, and covered with paxillae or spines ; feet conical ; 

 suckers inconspicuous or absent. 

 &i Arms long; feet without suckers; paxillae present....!. Astropectinidae 

 6a Body usually pentagonal ; epiproctal projection on aboral surface. 



2. PORCELLANASTERIDAE 



flj Aboral wall not membranous ; body often pentagonal ; feet with sucking discs. 



&i Aboral wall with closely fitting plates, mosaic-like 3. Goniasteridae 



6a Plates of aboral wall form a reticulum. 



Ci Body covered with a smooth, thick skin 5. Asteropidae 



Ca Body not covered by a thick skin 4. Oreasteridae 



Family 1. ASTEOPECTINIDAE. 

 Flattened starfishes with long, slender arms, with a membranous 

 aboral wall covered with paxillae (Fig. 969, C), with very large marginal 

 plates (Fig. 971, 2), which may carry long spines, with conical ambulacral 

 feet which lack the sucking disc, and usually without anus: 9 genera, 

 with more than 100 species. 



1. AsTROPECTEN Gray. Two rows of marginal plates, the lower row 

 with many spines, the upper row with granules or spines; no pedicel- 

 lariae: 60 species, in all parts of the world, 

 mostly littoral. 



.ife i. ;:#•.. V^fv- X- A. articulatus (Say). Each upper mar- 



\^ ginal plate near tip of arm with a small blunt 



^ -'' tubercle; size 20 to 25 cm.: New Jersey south- 

 wards, from the shore to 25 fathoms; often 

 Fig. 971— Small portion common. 

 Sn 'a?m''or ^SrolS^een A. duplicatus Gray. Upper marginal plates 



paxmaTr with erect, conical spines; size 15 to 20 cm.: 



uie'VowLr^ma'rJinf/pfltS North Carolina southwards; common in 6 to 15 

 fathoms. 

 A. calif ornicus Fisher (Fig. 971). Upper marginal plates without 

 spines or tubercles ; size 12 to 18 cm. : coast of California, in 10 to 240 

 fathoms ; common in Monterey Bay. 



2. Ltjidia Forbes. Only one row (the lower) of marginal plates; 

 pedicellariae usually present: 25 species, 10 in the Atlantic. 



L. clathrata (Say). Aboral surface with crowded paxillae; arms 

 much flattened; disc small; marginal plates narrow, 50 or more to an 

 arm; size 20 to 30 cm.: New Jersey to Florida; often very common. 



