90 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



The tentacle pores are very large and rounded and show on their 

 borders the little spines characteristic of the genus Ophiotrema; 

 these spines are very fine, conical, pointed, and rather long, but they 

 are very often broken off, and it is difficult to give their number as 

 well as their exact arrangement ; it seems to me that typically there 

 are three spines on the internal or radial border of the pore, while 

 another spine, often a little more strongly developed than the pre- 

 ceding, is found on the external border in front of the insertion of 

 the first arm spine. 



The specimen in alcohol has the disk rather dark on the dorsal 

 surface : the arms are much lighter, almost white. 



Affinities and distinctive features. The genus Ophiotrem& was 

 previously known only from two species, each represented by a small 

 number of specimens all of which are in a more or less poor state 

 of preservation. In the two species already known, O. alberti Koehler 

 and 0. gracilis Kcehler, the dorsal surface of the disk shows distinct 

 plates, each of which bears a small spine, while in the new species 

 it is impossible to distinguish any plates on this surface, and the 

 covering of the disk is composed of both granules and more or less 

 recumbent spines. This difference does not seem to justify a generic 

 separation, for the characters shown by the mouth papillae, by the 

 tentacle pores of the mouth and of the arms, by the arm spines, by 

 the upper and under arm plates, etc., agree very well with the char- 

 acters of the genus Ophiotrema. 



I have already had occasion to express my opinion on the subject 

 of the affinities of the genus Ophiotrema (Koahler '09, p. 196) ; con- 

 trary to Verrill's opinion, I believe that the genus Ophiotrema 

 is near the genus Ophiopora and not at all close to the genus Ophio- 

 mitra, as that naturalist has suggested, and near which he has 

 placed it. 



This affinity with the genus Ophiopora has been recently admitted 

 by H. L. Clark, but he goes much farther, for he unites the two 

 genera. In his catalogue of the ophiurans ('15, p. 218) he places 

 my 0. alberti and the genus Ophiotoma. I can not accept this point 

 of view, for I consider that the genus Ophiotrema is perfectly valid 

 and should be retained. I have accepted it as characterized by the 

 presence of small spines on the borders of the arm tentacular pores, 

 as well as by other structural features. This character is absolutely 

 lacking in the genus Ophiopora, where the pores are mostly quite 

 without scales. 



Matsumoto's opinion is quite opposed to H. L. Clark's, and he re- 

 tains the genus Ophiotrema as distinct from the genera Ophiopora 

 and Ophiotoma ('17, p. 93), the presence of the large tentacle pores 

 invoked by H. L. Clark to unite them being, he says, a character 



