WEST INDIAN STARFISHES 



11 



Forcipulosa they have very short pedicels, and they are most fre- 

 quently bivalved. 



They are of several different types, which are commonly char- 

 acteristic of the orders and families, and often of the genera. 



Sometimes there may be bivalved, trivalved, four-valved, and 

 five-valved ones on a single specimen, as in Dermasterias im- 

 hHcata. In some cases they are not really valvular, but consist 

 of several movable spinules, arranged in convergent groups or 

 opposed rows. The sessile valvular forms are generally situated 

 over a pore, penetrating a plate, for the passage of nerves, etc. 



Some of the special forms are described below, under the sev- 

 eral orders. 



In nearly all species there are numerous small, soft, tubular 

 outgrowths from the body-wall, called papidce, serving for respir- 

 atory purposes. They may be in large groups, especially be- 

 tween the dorsal and lateral ossicles, or stand singly, or they may 

 occur only in special areas. Rarely they are branched, as in 

 Luidia. 



Most shallow-water starfishes that have been studied in this 

 respect have a free-s^^dmming, bilateral larval form, known as a 

 brachiolaria. A considerable number carry their eggs and young 

 till they develop the starfish form. These have an abbreviated 

 metamorphosis. The two methods may occur in different genera 

 of the same family (e. g., Asteriidce) . 



The embrj^ology of the deep-sea species is unknown in most 

 cases, and may be diverse, or even more abbreviated. 



CLASSIFICATION OF ASTERIOIDEA. 



In this report I have adopted the division of the class into 

 three large orders, viz. : 



I. Forcipulosa or Forcipulata. 

 II. Spinulosa, with suborders, Avelata and Velata. 



III. PHxVNEROZONA. 



The last has three suborders, considered orders by some writers, 

 viz. : 



I. Valvulosa or Valvata. 

 II. NoTOMYOTA Ludwig (as an order). 

 III. Paxillosa. 



