MUSEUM OF COMPARATIVE ZOOLOGY. 261 



plates. They are lettered in Figs. 3, 4, and may be seen in Fig. 1, within the 

 side mouth-shields, against which they usually press, though in Ophiothrix they 

 are separated by an indentation. Sometimes they are covered by the skin or by 

 granulation (Opkiomyxa, Ophiura). 



d. Papillce orales vel marginales; saumpapillen ; papilles calcaires de labouche ; 

 mouth-papillae. These run along the lower edge of each mouth-angle, and the 

 greater part, or the whole, rest directly on the mouth-frames ; in a whole group 

 or genera they are wanting (Ophiothrix, Ophiocnemis, etc.). Ophiomyxa has them 

 under the form of little comb-like lobes. They are close and numerous in some 

 genera (Ophiocow.a), and confined to a single papilla on each side in others (Hcmi- 

 pholis). They run diagonally upward in some species of Ophioglypha. See also 

 under tentacle-scales. 



d". Papilhc dentales ; zahnpapillen ; tooth-papilla?. (Fig. 3, d', and the point 

 of the mouth-angle of Ophiothrix in Fig. 1.) This group of papilla?, lying just 

 under the teeth, is most developed in Ophiothrix, well marked in Ophiocoma, but 

 cpuite wanting in Ophiura. 



d". Dcntcs ; zahne ; teeth. (Figs. 3, and 4 d", and the point of the mouth-angle 

 in Ophioglyplia and Ophiura in Fig. 1.) These, like the tooth -papilla?, are always 

 carried by the jaw-plate, and are never wanting among true Ophiurans. In some 

 genera, they descend to the level of the lower margin of the jaw-frames (Ophio- 

 glypha, Ophiura, Ophiopeza), in others they are supplemented by tooth-papilke 

 (Ophiocoma, Ophiomasti.r, Ophiothrix)', and in Ophiomyxa they have the form of 

 comb-like lobes, resembling the rest of the chewing apparatus. 



e. Tones angularis j maxiller ; jaw-plate. (Figs. 3 and 4.) This is a narrow 

 calcareous plate, running vertically along the inner point of the jaws, with little 

 hollows in its surface, to which the teeth are bound by small muscles. It is 

 a part which always exists, and is made up of several pieces, which are often 

 separable. 



h. Scutella ventralia; bauchschilder ; plaques ventrales du bras; under arm- 

 plates. (Figs. 1 and 4, //.) They differ extremely in size and form ; being always 

 minute and more elongated at the tin of the arm, and in some genera they con- 

 tinue subordinate (Ophioglyplia, Ophiomusium), while in others they widen and 

 make a broad continuous strip (Ophiura, Ophiarachna, Ophiocoma). Some genera 

 have them covered by a thick skin (Ophiopsammium, (Jphioscolcx), as also Ophio- 

 myxa, where they divided, lengthwise, in two. 



i. Scutella lateralia : plaques laterales du bras ; side arm-plates. These may 

 be considered the fundamental covering of the arm, for they alone surround 

 it at the tip; and in one genus (Ophiomusium) they so continue nearly to its 

 base, almost wholly excluding the upper and under plates (Fig. 2, I i). Other 

 genera, like Ophioglyplia (Fig. 1, F i), have them persistent on the lower sur- 

 face of the arm, but replaced above by the upper arm-plates. Coming to forms 

 like Ophiocoyna, they are widely separated (Fig. 1, B) above and below. Fi- 

 nally,, in the extreme case of Ilcmicuryalc (Fig. 2, H i) the side arm-plates are 



