NO. 2 ZIESENHENNE : NEW OPHIURANS 35 



differs in having only 3 basal ann spines, shorter and stouter arm spines, 

 arms only twice the disk diameter, as compared to 5 times the disk di- 

 ameter, small, oval upper arm plates as compared to large, broad, rec- 

 tangular upper arm plates. The above characteristics distinguish this 

 species from other known related forms. In color it differs from Ophio- 

 nereis, which has regularly dark banded arms. The name amphilogus has 

 reference to the doubtful position of this species. 



Ophiolepididae 



Genus OPHIOMISIDIUM Koehler 



Ophiomisidium leurum, new species 



Plate 7, Figs. 1-3 



Description. — Disk diameter, 4 mm.; arms, 4 mm. long. Disk large; 

 arms short, tapering rapidly. Disk covered with 37 large, granulated 

 plates. Central plate pentagonal, surrounded by 5 quadrangular plates, 

 whose acute distal angles separate the proximal portion of the radial 

 shields. Separating the radial shields interradially are 2 plates, a rectan- 

 gular proximal plate and, distally, a produced, rounded, swollen plate 

 that fills the interbrachial margin and side of the disk. A rounded plate 

 and an oblong plate separate the distal margins of the radial shields. A 

 small plate (distal end of 2nd side arm plate) at the distal margin of 

 each radial shield, bearing 3 large spines, completes the side margins of 

 the disk. 



Radial shields oblong, almost twice as long as wide, separated proxi- 

 mally by the primary radial plate, broadly in contact medially but sep- 

 arated distally by 2 plates, one rounded and swollen above the surface of 

 the radial shields, the other much broader, not elevated, lying on the side 

 arm plates at the arm base. 



First upper arm plate very small, diamond shaped, succeeding plates 

 becoming still smaller distally until none can be found after the 4th arm 

 segment; plates widely separated by the side arm plates. First side arm 

 plates somewhat swollen, wider than long, meeting within, not visible 

 from above; 2nd plates are visible from above just distal to the radial 

 shields. Succeeding side arm plates narrower, becoming longer distally 

 and fully in contact. There are apparently not more than 10 or 12 arm 

 segments. Arm spines small, only 2 on first arm segment; there are 3 on 

 the next arm segment, well separated, uppermost heaviest, triangular, 

 blunt, longer than wide, median one or 2 shorter, lowermost shortest, 



