WEST INDIAN STARFISHES 85 



Pseudopaxillw are articulated plates with flattened, -usually 

 lobed, and often overlapping bases, which bear a group of slender, 

 fascicled or divergent spinules on the more or less raised central 

 or subcentral area or boss. These have no differentiated mar- 

 ginal series of spinules. This form is seen in Henricia, etc. 



In some families the plates are reticulated ossicles, smooth or 

 bearing large spines or tubercles as in Oreasteridce. In other 

 cases a thick skin may cover and obscure the plates. 



The interactinal plates may be few in slender stellate forms or 

 many in the pentagonal forms. In the latter cases they are 

 usually arranged in definite rows, most often subparallel with 

 the adambulacral plates, the latest formed ones being situated 

 next the median, interradial, marginal plates, but they also 

 form rows running from the adambulacral plates to the mar- 

 ginals, and often define fasciolated grooves. 



They are most commonly tesselated and granulated, or else in 

 the form of pseudopaxillae or protopaxillas ; but they are some- 

 times spinose. They may be more or less imbricated by their 

 edges or lobes. 



Adambulacral plates are not compressed, rather large, usually 

 oblong or quadrangular, and commonly bear numerous small 

 spines, various in arrangement. 



Ambulacral plates are rather large, not compressed nor crowd- 

 ed. Ambulacral feet are in two rows, with terminal suckers in 

 Valvulosa ; but in the Paxillosa they are large and pointed, with- 

 out distinct suckers. 



Pedicellariae are sometimes lacking, but usually present and 

 sometimes large. They may be bivalved, sessile, and seated over 

 a pore (foraminate), or implanted in special pits on the plates 

 (fossate) ; or else papilliform or fasciculate, composed of two to 

 four or more modified, convergent spinules; or pectinate, con- 

 sisting of two comb-like groups of spinules convergent over a 

 suture between two adjacent plates, as in Luidiaster, or seated on 

 a' single plate. 



The sessile valvular pedicellariae with a pore between the 

 valves are called foraminate ; they may have two, or more than 

 two, valves {hivalvular and trivalvul^r^ etc.). In the suborder 

 Valvulosa they are often provided with a pair of pits or fossae, 

 into which the valves fit when widely open. The valves in these 



