OPHIURANS OF THE PHILIPPINE AND ADJACENT WATERS. 117 



As 0. mutata was established on the basis of only three specimens, 

 and as 0. sagittata and 0. subjecta are both also represented by a 

 very small number of individuals, it is very difficult to appraise the 

 true value of the differences which I have given. Ophiomitrella sub- 

 jecta from stations 5280 and 5325 seems to me, on account of the ar- 

 mature of its disk, to differ more from 0. mutata than the individuals 

 which I have described under the name of O. sagittata. 



However that may be, it has seemed to me preferable to describe 

 under two different names the two forms collected by the Albatross; 

 they can be later considered as simple varieties of O. mutata if we 

 obtain new specimens showing intergrading forms. 



Under the name of Ophiomitrella stellifera Matsumoto has just 

 described ('17, p. 104) a Japanese species which seems to me also very 

 close to O. sagittata, O. subjecta, and O. mutata. The plates of the 

 disk bear rather broad club spines terminated by a stellate crown of 

 six spinules which seems very regular, the form of the mouth shields 

 is very different from that which I have described in the two species 

 collected by the Albatross, and the upper arm plates are also broader 

 and shorter than in 0. stelligera. 



OPHIORIPA, new genus. 



Description. — I have thought it necessary to create, near the genus 

 Ophiomitrella as defined by Verrill, another genus characterized by 

 having the disk covered with very large subequal plates which are 

 highly developed, especially in the central region, and which may at- 

 tain dimensions equal to or scarcely less than those of the radial 

 shields. These plates are thin, and, in the two known species of the 

 genus, they show about their periphery a narrow and transparent 

 border ; some of them carry granules or spines which are always few 

 in number. The radial shields, which are of medium size, are almost 

 as long as broad. The lateral mouth papillae, three in number, are 

 borne by the oral plates together with an unpaired terminal papilla. 

 The arms, which are slightly or not at all moniliform, are more or 

 less contorted ; the upper arm plates are of small size and separated 

 from the base of the arm outward by the side arm plates. The under 

 arm plates are also very small, widely separated, and only occupying 

 a small portion of the length of the arms. The arm spines are not 

 very long, and the two lateral series are widely separated in the 

 median dorsal line of the arms. 



Notes. — The genus Ophioripa differs from the genus Ophiomitrella 

 in the large dorsal plates of the disk, which are provided with a 

 transparent border, in the very small under arm plates, and in the 

 wide separation along the median dorsal line of the arm of the col- 

 umns of arm spines. It is distinguished from the new genus Ophioph- 

 thalmus, recently established by Matsumoto and of which I shall 



