Invertebrate Gallery of the Indian Museum. 99 



by spiny or granular plates of lime. On the under sur- 

 face of the disk we find, in the centre, a large mouth, and 

 radiating from the mouth five channels or furrows — the 

 ambulacral furrows — from which the ambulacral tube- feet 

 by means of which the Star-fish progresses, emerge in rows. 

 On the upper surface of the disk we find, in the centre, 

 usually but not always, the anus, and near the margin 

 of the disk and between two of the rays, the madreporic 

 plate. In some forms there is more than one madreporic 

 plate— ^.^., the Acanthaster, in Case 24, has eight. In some 

 forms — e.g., Astropecfen — there is no anus. The more 

 apparent details of the internal structure of the Star-fishes 

 (such as the arrangement of the water-vascular system, the 

 stomach with its pouches extending into the rays, the genital 

 glands, etc.) are shown in several dissections to which 

 explanatory notices are attached. 



The Star-fishe sare all marine, and live at all depths, 

 from the tide-marks down to depths of nearly three 

 thousand fathoms. The shallow-water species prefer hard 

 ground, such as rocks and reefs and beds of hard sand, 

 where they find in abundance the Mollusca and the small 

 Crustacea upon which they feed. The deep-water or 

 abyssal species dwell upon the ooze of the ocean-bottom, 

 and some of these species appear to gorge themselves 

 with the ooze for the sake of the minute particles of 

 living or dead animal-matter that it contains. Many 

 species of Star-fishes are gregarious — that is to say they 

 live together in large swarms ; and some species have been 

 observed to pair at the breeding season. In one family 

 of Star-fishes, of which the magnificent specimen of Hymen- 

 asternobilis in Case 23 is an example, the eggs are carried 

 about in a nest-like pouch on the back of the animal until 

 the young are hatched. 



The Asteroidea are represented by species of the 

 following genera, all from the Indian Seas :^ 



(i) From the littoral, and from shallow-water :—' 

 Ar chaster; Craspidaster^ Astropecten, Luidia, Stellaster, 



