122 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



fera Liitken and Mortensen, Ophiomitrella placida Kcehler, and 

 various others, but I differ completely from him regarding the limits 

 of the genus Ophiophthalmus and the species which should be 

 assigned to it. 



The species which are included by Matsumoto in the genus 

 Ophiophthalmus, thirteen in number, are in the following : 



Ophiomitrella americana Kcehler. 

 Ophiomitrella mutata Kcehler. 

 Ophiomitrella languida Kcehler. 

 Ophiacantha cataleimmoida H. L. Clark. 

 Ophiacantha normani Lyman. 

 Ophiacantha relict a Koehler. 

 Ophiomitra granifera Liitken and Mortensen. 

 Ophiacantha leucorhabdota H. L. Clark. 

 Ophiacantha eurypoma H. L. Clark. 

 Ophiacantha hylacantha H. L. Clark. 

 Ophiomitra codonomorpha H. L. Clark. 

 Ophiomitrella placida Koehler. 

 Ophiomitra microphilax H. L. Clark. 



First of all, I believe it necessary to remove from the genus 

 Ophiophthalmus three of these species. First, Ophiomitrella ameri- 

 cana; I do not see any plausible reason for not leaving this in the 

 genus Ophiomitrella, of which it shows all the generic characters ; it 

 is furthermore very close to 0. granulifera Kcehler, which Verrill 

 assigned to the genus Ophiomitrella when it was established. I 

 may say as much of O. mutata and O. languida, which seem to me 

 to find their place much better in the genus Ophiomitrella than in 

 Matsumoto's new genus. 



The other species it seems to me possible to separate into three 

 groups. The first of these groups includes first the type chosen by 

 Matsumoto for his genus Ophiophthalmus, which is Ophiacantha 

 cataleimmoida, then the species which are close to it, that is to say, 

 O. normani, 0. granifera, and 0. relicta. In none of these species, 

 not even in the type of the genus, do the arm spines show the 

 characters indicated by Matsumoto in his diagnosis — "numerous, 

 long, conical, opaque, hardly serrate" — for these spines are not 

 elongated, and they are not numerous; O. cataleimmoida has six, 0. 

 normani four, 0. granifera six, and 0. relicta five or six, and they 

 are provided with denticulations in the last two species. These four 

 species possess the common character of having the dorsal surface 

 of the disk covered with rounded grains which are found on the 

 distal edge of the upper arm plates for a greater or lesser distance 

 along the arms. The radial shields are large, or at least rather large. 



The second group also includes four species ; these are Ophiacantha 

 leucorhabdota, 0. eurypoma, 0. hylacantha, and O. condonomorpha. 



