Natural History of Molluscous Animals, 71 



The Crinoidea, connected with the starfishes by the oscu- 

 lant forms of the Gorgonocephali, must now receive the 

 Comatulae : one section containing the sublocomotive Coma- 

 tulae ; the other, and greater, division embracing the various 

 genera so well described and plainly figured by Mr. Miller, 

 and the Pentacrinus of Thompson [figured and remarked on 

 in our II. 114, 115.], which have the base attached to various 

 bodies, and their want of locomotion compensated by the 

 unusual length of the vertebriform column. In all these the 

 surface of articulation is carved, and beautifully radiate. It 

 has been doubted whether the vertical spot in ^sterias affords 

 any passage through the crust. In dried specimens it may 

 appear not to be the case, as the spot becomes as much in- 

 durated as the general crust ; but the zoologist, who contem- 

 plates the harder species alive, and observes the facility with 

 which they, when overturned, contort and alter the shape of 

 their rays, in order to recover their position, will easily believe 

 that the disc is really perforated. I have never seen the 

 faeces expelled through this rude contractile orifice; and it 

 may, possibly, be only connected with the ovary. In a sub- 

 genus figured in the Supplement to Parry's Voyage, 1824, if 

 one can depend upon the engraver, the aperture is terminated 

 by a perforated bulb : the spot beneath it I do not profess to 

 understand. — [L. Guilding. St. Vincent, May 1. 1830.] 



Art. III. An Introduction to the Natural History of Molluscous 

 Animals. In a Series of Letters. By G. J. 



Letter 15. On their Food and Digestive Organs: Herbivorous 



Mollusca. 



The herbivorous, or, as they are frequently named, the 

 phytophagous, Mollusca belong exclusively to the class of 

 gasteropodes, and embrace, with few exceptions, the Pulmo- 

 nifera, the Nudibranchia, the Inferobranchia, the Scuti- 

 branchia and Cyclobranchia, a great proportion of the Tecti- 

 branchia, and all the Pectinibranchia which have no slit or 

 siphon in the collar of the mantle, or, which is the same 

 thing, whose shell has an entire aperture.* What proportion 

 these united may bear to the zoophagous, it is impossible to 

 say ; for we are not in possession of a complete catalogue of 



* The families Trochoides and Capuloides of Cuvier. (Reg. A?iim., iii. 

 72. 86.) Adanson has given the distinguishing characters between the 

 zoophagous and phytophagous pectinibranchial Mollusca very correctly. 

 {Hist. Nat. du Senegal, p. 80, 81. 193.) 



f 4 



