90 D1SC0PH0R.E. Part III. 



are commonly called the fringes of the mouth.^ Plate IV. represents the lower 

 surface, fully expanded ; yet, to avoid confusion, the parts that are visible in the 

 natural state of this animal are not all i-eproduced, but only one bunch, or one set 

 of each kind, the others being omitted. The parts preserved are so selected as to 

 give an accurate idea of the resjjective position of all the different organs, and 

 some are laid out in a manner which may explain their structure more fully than 

 the complete profile figure of Plate III. In the first place, the quadrangular open- 

 ing in the centre, or what is commonly called the mouth, would not be visible at 

 all, had the four masses of curtain-like folds, which hang from its outer edge, been 

 all preserved, and on that account only one and one half of another are repre- 

 sented ; but even these are not shown foreshortened and folded, as they should be 

 when the animal is turned mouth downward ; they are, on the contrary, flattened out, 

 so as to show the furrows which extend along the middle of each, from the corners 

 of the so-called mouth to their lower edge. Owing to this artificial position, several 

 parts which hang from the lower surface of the disk are concealed ; but identical 

 parts are exhibited in other directions, where the other lobes of the mouth are cut 

 away. Of the ovarian bunches, only one is represented, and it will easily be noticed 

 that it occupies the space between two angles of the mouth, so that the four bunches 

 of mouth fringes and the four bunches of ovaries alternate \ipon eight diverging 

 rays, extending from the centre of the disk to its margin; but, as PI. III. clearly 

 shows, the mouth fringes hang lower down than the ovarian bunches. Again, of 

 the eight bunches of threads one only is represented in PI. IV. Fiff. 1, and the 

 others are either entirely omitted, or their base of attachment only indicated; but 

 from the position which they occupy, it is at once plain that each bunch alternates 

 with the eight spaces intervening alternately between a bunch of mouth fringes, 

 and an ovarian bunch ; so that the four mouth fringes, the four ovarian bunches, 

 and the eight bunches of threads, occupy sixteen different imaginary rays, extending 

 from the centre to the periphery of the disk. It is important that the reader 

 should make himself familiar with this remarkable arrangement before jiroceeding 

 further, for it constitutes one of the essential features in the symmetry of this animal. 



* As the introduction of letters or figures to altogether; but I trust the attentive reader will 



designate the different parts of the plate would have easily connect the description and the plates in his 



injured its appearance, if they had been sufficiently mind, and thus supply the reference, 

 numerous to mark them all, I have omitted them 



