. Seaside studies in natural history. Marine animals. 108 MAEINE ANIMALS OF MASSACHUSETTS BAT. bijstles entirely removed, the lines of sutiire of the plates com- posing it, and corresponding exactly to those of the spherical Sear-urchin, may very readily be seen, (a and i, Pig. 139.) This flat Sesrurchin or Echinarachnius, as it is called, belongs to a group of Sea-urchins known as Clypeastroids (shield-like Sea-urchins). In a section (Fig. 140) exposing the internal structure, one cannot but be reminded by its general aspect of J,. ^^ an Aurelia. Could one solidify an Aurelia it would present
. Seaside studies in natural history. Marine animals. 108 MAEINE ANIMALS OF MASSACHUSETTS BAT. bijstles entirely removed, the lines of sutiire of the plates com- posing it, and corresponding exactly to those of the spherical Sear-urchin, may very readily be seen, (a and i, Pig. 139.) This flat Sesrurchin or Echinarachnius, as it is called, belongs to a group of Sea-urchins known as Clypeastroids (shield-like Sea-urchins). In a section (Fig. 140) exposing the internal structure, one cannot but be reminded by its general aspect of J,. ^^ an Aurelia. Could one solidify an Aurelia it would present much the same appearance ; another evi- dence that all the Radiates are built on one plan, their differences being only so many modes of ex- pressing the same structural idea. The teeth or jaws in this flat Sea- urchin are not so complicated as in the Toxopneustes, being simply flat pieces, arranged around the mouth (o, Fig. 140), without the apparatus of muscular bands by means of which the teeth are moved in the other genus. It is a curious fact, considered in relation to the general radiate structure of these animals, that the teeth, instead of moving up and down like the jaws in Vertebrates, or from right to left like those of Articu- lates, move concentrically, all converging towards the STAE-FISHES. Star-fish. (Astracanthion herylinus Ag.) Although there is the closest homology of parts between the Star-fish and the Sea-urchin, the arrangement of these parts, and the external appearance of the animals, as a whole, are entirely dififerent. The Star-fish has zones corresponding exactly to those Xlg. 140. TraoBverse section of Bchinarachnius ; O'Viouth, e e ambulacra, c m ambnJacral ramificft. tloiiB,wu>interambulacra. (^gaaaiz.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Agassiz, Eliza
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectmarineanimals, bookye
