658 Div. 4. RADIATA.— ECHINODERMATA. Class 1. 



the general characters of the genus Astenas, the Star-fish, properly so called ; and, in proportion as 

 they deviate from the Five-rayed Star, their coeca and ovaries are more numerous. 



A. rubens, is very common in the European seas. A. glacialis, is much larger, often a foot in diameter; and 

 it has tufts of fleshy tubes round the bases of the spines on the body. A. auraniia, is still larger, and has the 

 edges of the rays paved -with osseous plates, bearing strong and moveable spines. Some, as A. paposa, have 

 more than five rays. Some have the rays solid, and without the groove, and they are called Ophiunc, because 

 their rays have some resemblance to the tails of Serpents. These move by flexures of the rays, which have spines 

 on the sides in some, and are covered with imbricated scales in others. In them the pores are between the bases 

 of the rays. The only feet vrhich these have are in fine short grooves round the mouth. By some authors they 

 have been made a separate genus. Some have the rays branched, and of them some have the division near the 

 end of the rays, and seldom repeated ; but in others it begins at the base, and each division is branched again 

 and again, till the whole resembles a bunch of Serpents' tails ; each branching is into so many lateral parts : there 

 ai'e two points at the base of each ray. Those branched ones have been called Gorgonocephalcc, or Medusa's 

 Heads. 



Alecto, or Comatula, have five large articulated rays proceeding from a stony plate on the upper part of the 

 disc ; their rays are often divided into two or three branches, and both rays and disc are furnished with articu- 

 lated threads. The cavity of the body has a star-shaped mouth, and a tubular opening, both on the under side. 



Encrinus [the Encrinites],— 

 Resemble the last, but have the plate on the disc prolonged to a stem of many articulations. They are named 

 from the form of the stem, and the number of rays. Pcntacrimis curopcetis, is the only species in the European 

 seas ; but there are others in the tropical oceans. In a fossil state they are exceedingly numerous, and varied ill 

 their appearance. The fossil Entrochites are portions of the stems or branches of Encrinites. 



THE SECOND FAMILY OF THE PEDICELLATA. 



The Echinus [Sea Hedge-hogs, or Sea Eggs]. 



These have the hody covered with a crust of calcareous matter, in segments nicely adapted to each 

 other, and perforated by regular rows of holes for the membranous feet. The crust is also pierced by 

 a number of smaller holes with four membranous tubes, which seem to be the breathing apparatus ; 

 and where not perforated, the crust is armed with broad spines, articulated upon tubercles, and move- 

 able. The mouth is furnislied with five flat, calcareous teeth, in a very complicated apparatus, and 

 having strong muscles ; and, as these wear away at their cutting edges, they extend by growth at the 

 opposite extremity. The intestine is long, and attached spirally to the interior of the crust. The five 

 ovaries, which are edible, are arranged round the vent, in the separate openings. Their motions 

 are slow ; and they feed upon the smaller shelled Mollusca and Crustacea, which they seize with their 

 membranous feet. Great numbers of them, including many not now found alive, are met with in a 

 fossil state, especially in the chalk, where they are usually filled with flint earth, the same as the 

 sponges. 



They are either regular or irregular, — the regular ones having the mouth in the middle of the under 

 side, and the vent opposite ; and the others arc irregular in proportion as they deviate from this 

 character. 



Echinus, properly so called. — Figure generally nn oblate spheroid, with two bands of apertures, dividing the 

 surface from the mouth to the vent into segments, resembling those fornu'd by the meridians on a globe. Some 

 have the spines stout, with smaller ones at the base, and others have them slender. Among the latter, is E. cscit- 

 Iciitits, found in the Eurojiean seas. It is about the size of an ordinary apple, closely set with short spines, gene- 

 rally of a violet colour. The ovaries are of the same colour; and in the spring months they are edible, and have 

 a very agreeable flavour. 



They vary in shape, and in the number and arrangement, and also the form of the spines. Some are depressed, 

 some compressed, some have the spines unequal, and one species, E. atraius, has the spines unequal and trun- 

 cated, resembling small paving-stones. 



None of the irregular ones have the two apertures of the body opposite to each other in the middle 

 of the under and upper sides. The spines upon them are straight and slender; and the chief distinc- 

 tions are the number, arrangement, and extent of the holes for the feet. 



C/iironcus, have the general form of the last, but the mouth and vent are both on the under side. 



jS'udcolilcs, liave the vent above, but near the margin. 



GttlerUes, have a flat base, and a conoidal body, with the mantle in the centre of the disc, and Ihe vent near its 

 margin. 



HciihUd, have the openings as in tlic last, but the form of the body much depicssed, and disc -like. Some have 

 DO openinss to the crust but the pores, and in othws again these seem to be oblitcr;i'"d, or at all e\cnts do not 



