640 ECIIINODERMATA. 



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

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



,(. ritliohs, is very common in the European seas. A. (/facialis, is much larger, often a foot in diameter; anJ 

 it h,T,s tufts of fleshy tubes round the bases of the spines on the body. A. aurantia, is still ]arg;er, and has the 

 e(li:es of the rays paved with osseous plates, bearing:; stront;; and moveable spines. Some, as A. paposa, have 

 more than fi\'e rays. Some have the rays solid, and without the f^roove, and they are called Ojw///;/rtf, 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 which these have are in fine short grooves round the mouth. By some authors they 

 have beon made a separate g;enus. 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 beo;ins at the base, and each division is branched again 

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

 are two points at the base of eacli i*ay. Those branched ones have been called Gorgonocvphala, or Medusa's 

 Heads. 



AleciOy or Cnuiaii'hi, have five lar,e:e articulated rays proceeding from a stony plate on the upper part of the 

 disc ; their ravs air' ui'ti. n divided into two or three blanches, and both rays and disc are furnished with articu- 

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



Encrinus [the Encrinites], — 

 Resemble tlie last, but have the plate on the disc prolonged to a stem of many articulations. They an lamed 

 fi'om the lorrn of tlie stem, and the number of rays. Pentacrirms europceus, is the only species in tlie Eurooean 

 seas ; but there are others in the tropical oceans. In a fossil state they are exceedingly numerous, ana vaned m 

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



THi^ SECOND FAMILY OF TFIE PEDICELLATA. 

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

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



otlicr, and perforated by regular rov^s of holes for the membranous feet. The crust is also pierced by 

 a numher of smaller holes with four memliranous tubes, which seem to he the breathing apparatus; 

 and where nut perforated, the crust is armed with broad spines, articulated upon tubercles, and move- 

 ahlc. Tlie niuiith is furnished with five flat, calcareous tcelh, in a very complicated apparatus, aii:l 

 Ijaving strong ran cles ; and, as tliese wear away at their cutting edges, they extend by growth at ";as 

 opposite extremity. The intestine is long, and attached spirally to the interior of the crust. Th-e *ive 

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

 are slow ; and thry feed upon the smaller shelled Mollusea and Crustacea, which they seize with th?ir 

 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 

 s}ionges. 



They are either regular or irregular, — the regular ones ha\ing the mouth in the middle of the under 

 side, and the vent o])i)Ositc ; and the others are irregular in proportion as they deviate from this 

 character. 



Erhinusy properly so called.— Figure generally an oblate spheroid, with two bands of apertures, dividing tne 

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

 ha\'e the spines stout, with smaller ones at the base, and others have them slender. Among the latter, is E. cscu- 

 I'lifus, found in the European 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 mouths they are edible, and have 

 a \ery agreeable flavour. 



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

 siiTiie compressed, some ha\'e the spines unequal, and one species, E. (itrafus, has the spines unequal and trun- 

 cated, resembhng small paving-stones. 



None of t!ic irregular ones have the two apertures of the Ijody opposite to each other in the luiddle 

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

 ti(uis air the number, arrangement, and extent of the holes for the feet. 



L'liironeus, have the general form of the last, but the mouth and vent are both on the under side. 



NucholUes, have the vent above, but near the margin. 



Gnleritcs, have aflat base, and a conoidal body, with the mantle in the centre of the disc, and the vent near its 

 margin. 



iScufr//n, liave the opiotiiiigs ns in the last, bnt the form of the body much depressed, ami disc-til<'\ Some have 

 no openings to the crust btit tlie pores, and in others again these seem to be obliterated^ or at all events do n-st 



