90 PROCEEDINGS OF THE ACADEMY OF [Feb.^ 



but the depth is not stated. As the annulation on the arms indicates^ 

 this species is not a deep-water form, but probably subUttoral. 



Subfamily 2. OPHIONEREIDIN^ Ljungman, 1867 (emend.). 

 (Characters as given in key, p. 88.) 

 Tliis subfamily includes Ophiodoris, Opkionereis and Ophiocrasis. 



OPHIOCRASIS H. L. Clark, 1911. 



Aside from the presence of the secondary supplementary dorsal 

 arm plates, this genus seems to me to be distinguished from Opkio- 

 nereis principally by negative characters and different degrees of 

 development of certain common structures. Disk scales even and 

 exceecUngly fine; no trace of marginal row of special disk scales; 

 no genital papillae; arms much more slender than in Opkionereis. 

 Schizogonic reproduction may not be a generic character. 



Ophiocrasis marktanneri sp. nov. 



Ophionereis porreda, Marktanner-Turneretscher (non Lyman, 1860), Ann. 



K. K. Naturh. Hofmus., II, 1887, p. 302, PI. XII, i\%. 18. 

 "Ophionereis porreda Marktanner, " Koehler, Bull. Sci. Fr. Belg., XXXI, 



1898, p. 76. 



Diameter of disk 9 mm. Length of arms 68 mm. Width of 

 arms, at base 1.2 mm, at the widest part 1.5 mm. Disk circular, 

 slightly concave, rather soft, covered with fine imbricating scales, 

 which are rather obscured, so that the disk appears as though covered 

 by a thick skin. Radial shields very small, short, exceedingly 

 narrow, tapered within, widely separated from each other, hard to 

 detect. Ventral interbrachial areas covered with scales similar to 

 those of the dorsal side, but even more obscure. Genital slits large, 

 nearly reaching disk margin. No genital papilla?. 



Oral shields rhomboidal, with obtuse inner angle and rounded 

 lateral and outer angles, nearly as wide as long, except madreporic 

 shield, which is decidedly longer than wide. Adoral shields small, 

 acutely tapered within, where they nearly or hardly meet. Four 

 or five oral papillae on either side of each jaw, unequal, short, rounded, 

 but the outermost one, which is closely associated with the second 

 oral tentacle pore, has pointed inner end. Four teeth, short, stout, 

 with wide end. 



Arms long and very slender, narrowed at base, widest at one- 

 fourth to one-third of arm length. Dorsal arm plates mostly tri- 

 angular, with obtuse outwardly directed apex, rather small, wider 

 than long, successive plates slightly in contact with each other; 

 quadrangular in the more distal parts. On either side of each dorsal 

 arm plate there occurs a large supplementary plate, which is nearly 



