SAJfD-STARS AND STAR.FISHE8. Ill 



beach. It is variable in color, but beautifully spotted with 

 pale and brown, its general hue being a brick-red. Am- 

 phiura squamata Sars has long slender arms and is 

 white ; it lives below tide-marks. The basket-fish, me- 

 dusa's head, or Astrophyton 

 Agassizii Stm., is of large 

 size, the disk being two in- 

 ches across, and the arms 

 subdividing into a great 

 number of tendril-like 

 branches. It lives from ten 

 to one hundred fathoms in 

 the Gulf of Maine. 



Ophiurans are widely dis- 

 tributed, and live at depths 

 between low- water mark and 



two thousand fathoms. POS- rig. l^.-OplmpholUbdlls, common Sand- 



sil Ophiurans do not occur ^'"-^te^ Morse. 

 in formations older than the Upper Silurian, where they are 

 represented by the genera Protaster, Palmodiscus, Acroura, 

 and Eucladia ; genuine forms closely like those now living 

 appear in the muschelkalk beds of Europe (Middle Trias). 



Order 2. Asteridea. — In the true star-fishes the arms are 

 direct prolongations of the disk, and the stomach and 



Fig. 73.— Three foi-me of Star-fish, A, B, C, seen from above, showing the different 

 development of the amhulacral and interanibulacral areas. The ambulacra are indi- 

 cated by rows of dots ; o, mouth; r, arms; ir, interradial or interambulacral areas. 

 V Pteraster; B, Goniodiscus; A, Aste?iscus.—Mt{:r Gegenbaur. 



ovaries or spermaries project into tliem^ and there is a deep 

 ambtilacral furrow, while the interanibulacral spaces vary 

 much in development (Fig. 73) ; the feet are provided with 



