495 



ECHINODERMATA. 



ECHIODON. 



There are other parts, apparently of great consequence in the 

 organisation of the animal, which are common only to certain members 

 of the order. These are the brachial appendages (arms and tentacula) 

 and certain curious organs connected with the plates, to which the 

 name of ' pectinated rhombs ' may be appropriately given. (Forbes.) 



The result of Professor E. Forbes's labours are given in the follow- 

 ing Table of Fossil Attendee : 



The following is an arrangement of the genera of British Cyitideie 

 found in the Silurian Rocks : 



A. Bodies composed of definite numbers of plates. 



a. With arms and pectinated rhombs. (Upper Silurian.) 



Pieudocrinitei. 

 'Apiocyititti. 



b. Armies?, with oval tentaculated and pectinated rhomb*, 



(Upper Silurian.) 



Prunocyttitei.) 



c. Armless, with oral tentacula wanted ; pectinated rhomb 



present. (Upper Silurian.) 

 Eeh ino- Encrin an. 



d. Armlew, no rhombs j bodies composed of four series of 

 plates, exclusive of the oral plates. (Lower Silurian.) 



Ifemicosiiiites. 



e. Armless, no rhombs ; bodies composed of more than four 

 series of plates, exclusive of the oral plates. (Lower 

 Silurian.) 



Caryocystites. 

 B. Bodies composed of an indefinite number of plate?. 



a. With arms, no rhombs. (Lower Silurian.) 



Agelocrinites. 



b. Without arms, no rhombs. (Lower Silurian.) 



Various views have been entertained by naturalists as to the 

 nature of these bodies. Linnaeus, from the polygonal forms of the 

 plates with which they are covered, regarded them as minerals. From 

 the time however that their animal nature was admitted, they have 

 been regarded by most writers as belonging to various groups of the 

 Echinodermata. Mr. M'Coy has suggested their resemblance to certain 

 forms of Astidia, but Professor E. Forbes regards this resemblance 

 as one of analogy only. In the Monograph above referred to, Professor 

 Forbes thus arranges the Cystidece amongst the Echinodcrmata, : 

 ECHINID.E. ASTERIAD.E. 



CBINOIDK.!;. 



"In this diagrani," siiya Professor. Forbes, "the word CYSTIDE.E 

 occupies the centre, and around it are the names of the several genera of 

 undoubted Cyrtidcans printed in small Roman letters, and arranged iu 

 the order of their affinities. Between them, however, and the names 

 in small Roman capitals indicating the great groups of equal value with 

 the CTSTIDEJ:, are other names of genera printed in italics. These 

 are the genera which seem to me to link the Cystideans with the 

 members of the other great sections of Echinodcrmata. The lowest of 

 these is the remarkable fossil Caryocrinut, admitted on all hands to 

 afford a distinct passage from the Crinoids to the Cystideans, as far as 

 there can be a distinct passage between two great orders." He then 

 proceeds to point out in detail the relations of the various genera 

 referred to with each other and with the families at the top of the 

 diagram. 



ECHINOUI'SCUS. [ECHINIM.] 



ECHINOLA'MPAS, a genus of fossil EMnida, from the Oolitic 

 and Chalk Strata. [ECHINODEBMATA.] 



ECHINOME'TRA. [EcHijriD^.l 



ECHINONE'US. [ECHIXIDA] 



ECHINO'PHORA (from Ixfrn, a hedgehog, and $opos, in composi- 

 tion signifying ' bearing'), a genus of Plants belonging to the natural 

 order Vmbelliferce, and to the tribe Smyrnea. It has a calyx of five 

 teeth, th petals obcordate with an indexed point, the exterior largo 

 and bifid ; the flowers of the ray sterile on long stalks, the central 

 fertile and solitary ; the fruit ovate terete, embedded in the enlarged 

 receptacle ; the carpels with five depressed equal striated wavy ridges ; 

 interstices with single vitta, covered by a cobweb-like membrane. The 

 S. tpinota, the Sea-Parsnip, has been admitted into the British Flora, 

 but it must be considered a doubtful native. It has been found in 

 Lancashire and Kent. It is mostly an inhabitant of sandy sea-shores, 

 and has pinnate spinose leaves, and resembles in habit and external 

 character the Erynyium. Three other species are described. When 

 cultivated they require a warm situation and a dry soil. They must 

 be propagated by cuttings of the roots or stems. (Don. Dichlamydeom 

 Plants.) 



ECHINORHI'NUS. [SQUALID*.] 



ECHINORODON. [ECHINID*.] 



ECHINO'STACHYS, a genus of Fossil Plants, from the Bunter 

 Sandsteiu. (Brongniart.) 



ECHINUS. [ECHINID.K] 



ECHIODON, a genus of Apodal Malacopterygious Fishes belonging 

 to the family Munenidv. The head is oval; jaws furnished with 

 large cylindrical teeth in front ; other smaller teeth on the palatal 

 bones and on the vomer. Gill-apertures large ; branchiostegous mem- 

 brane with seven rays. Body smooth, without scales, elongated, com- 

 pressed. Dorsal and anal fins nearly as long as the body ; all the 

 rays soft ; no ventral fins ; anal aperture near the head. 



