CLARK: BRITTLE-STARS. 271 



Of these I have examined specimens of nine. I have compared these 

 critically with each other and with the figures and descriptions of the 

 remaining species, and am satisfied that Ophiophragmus is a natural 

 group of tropical American amphiurans of which there are at present 

 known eight species. 



The following table shows the conclusion reached regarding each of 

 the forms hitherto referred to Ophiophragmus. 



affinis Duncan, 1887. An Amphioplus, identical with A. relictus Koehler. 

 andreae Matsumoto, 1915. Described by Lutken as Amphipholis andreae, 



seems to be an Amphioplus. 

 antarcticus Ljungman, 1867. Position doubtful; the minute disk-scales and 



small radial shields are against its being an Ophiophragmus; probably 



an Amphiodia. 

 brachyactis H. L. Clark, 1915. ?Valid. 

 diffidlis Duncan, 1887. Position doubtful; probably an Amphioplus but 



much like Ophionephthys in important particulars. 

 echinatus Ljimgman, 1867. An Ophiocnida. 

 gibbosus Ljungman, 1867. Position doubtful; the 4 oral papillae indicate an 



Amphioplus. 

 hispidus Ljungman, 1867. Described by Leconte as Ophiolepis hispida; seems 



to be an Ophiocnida. 

 japonicus Matsumoto, 1915. An Amphioplus. 

 loveni Ljungman, 1867. An Ophiocnida. 



marginatus Liitken, 1859. ?Vahd. Described as an Amphiura. 

 periercia Matsumoto, 1915. Described by H. L. Clark as Amphiodia peri- 



ercta; in that genus, I still think it belongs. 

 praestans Matsumoto, 1915. Described by Koehler as Amphiura praestans; 



seems to be an Amphioplus. 

 scabriiisculus Ljungman, 1867. Described by Lutken as Amphiura scabiuscula; 



seems to be an Ophiocnida. 

 septus Liitken, 1859. Valid. Described first as an Amphiura. 

 wurdemanii Lyman, 1860. VaUd. Described first as an Amphiura. 



There are four species, not hitherto referred to Ophiophragmus, 

 which unquestionably belong there. ^ These are Amphipholis luikeni, 

 Ljungman, Ophiocnida filogranea Lyman, Amphipholis erecta Koehler 

 and Ophiolepis chilensis M. & T. The first and third of these have 

 been admirably described and figured by Koehler, (1914. Bull. 84 

 U. S. N. M., p. 67-70, pi. 6) and specimens of each were taken in 

 Buccoo Bay, Tobago in April, 1916. Study of my Tobagoan material 

 soon convinced me that both species belong to Ophiophragmus and 

 that they are quite distinct from each other and from 0. wurdemanii 

 also. But I have not been able to find any differences between 0. 



