2 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



have therefore included figures of several, so that perhaps it may be 

 found that I have gone a little too far in some instances. In as- 

 sembling the illustrations I have paid particular attention to the 

 species of Ophiothrix; I have hoped thus to render a service to my 

 colleagues in indicating the very considerable variations met with in 

 this genus within which specific differentiation is exceptionally diffi- 

 cult. 



The representation of complete specimens, or at least of the entire 

 disk together with some of the arms for a greater or lesser part of 

 their length, seems to me indispensable in order to give an exact idea 

 of any ophiuran. In most of the memoirs in which I have figured 

 ophiurans by means of plates drawn by myself and reproduced 

 lithographically I have followed the example of Lyman, who repre- 

 sented the species merely by the portion of the disk included between 

 two arms, together with the basal portion of the latter. Obviously, 

 this method is convenient, and, above all, economical, but these in- 

 complete figures do not give a sufficiently comprehensive idea of the 

 animals, and I therefore definitely abandoned it some years ago. 



It has appeared advisable to include a certain number of photo- 

 micrographs representing the club spines, granules, etc., which occur 

 upon the disks of various ophiurans, particularly of the families 

 Ophiacanthidae and Ophiotrichidae, and which often assume char- 

 acteristic shapes. I have also included some photographs of the arm 

 spines of the species of Ophiotrichidae, particularly of the first ven- 

 tral arm spine, of which the hooklike form shows interesting varia- 

 tions. 



The following species are represented in the collection ; new species 

 are given in small capitals : 



Order I. PHRYNOPHIURIDA 



Family OPHIOMYXIDAE Ljnnjmian. I860. 



. 



Ophiomyxa bengalenms Koehler. 

 Ophiomyxa irregularis Koehler. 

 Ophiodera neglecta Koehler. 

 NEOPLAX CRASSIPES, new species. 

 OPHIOCANOPS FUGIENS, new genus and species. 

 OPHIOBYRSET.LA INTOBTA, new specios. 

 OPHIOPHRIXUS CONFINIS, new species. 



Family TRICHASTERIDAE Doderlein. 1911 (emended Matsuinoto, 1915). 

 Astrocharis virgo Koehler. 

 Astrocera* pergamena Lyman. 

 Asteronyx loveni Mtiller and Troschel. 



Family GORGONOCEPHALIDAE Doderlein, 1911. 



ASTROTHAMNTTS DKFTCIKNS. new 



