326 ART, 2. — H. MATSÜMOTQ : 



all well developed, with cereous lustre. Two to four, usually three, 

 arm spines, moderately long, erect. One or two large, leaf-like 

 tentacle scales on the abradial border of each pore ; sometimes 

 one to three very small accessory ones may occur on the adradial 

 border. 



This family includes five genera, whicli may be grouped into 

 two subfamilies as follows. 



Subfamily 1. Oplnoclntoninœ Maïsumoto, 1915. — Oral frames 

 without well developed lateral wings ; teeth triangular and obtusely 

 pointed ; dorsal surface of vertebrae entire, rhomboidal. 

 Ophiochiton Lyman, 1878.^^ 

 Opliioplax Lyman, 1875. 

 Subfamily 2. Ophionereidince (Ljungman, 1867) mihi, 1915. — 

 Oral frames with well developed lateral wings ; teeth very stout, 

 quadrangular, with truncated end ; dorsal surface of vertebrae 

 notched at the inner end and V-shaped. 

 Ophiodoris Kœhler, 1904. 

 Ophionereis Lütken, 1859. 

 Ophiocrasis Claek, 1911. 



As shown in the foregoing diagnoses of the subfamilies, there 

 are two types of internal structures in the present family. The 

 internal structures of the Ophiochitonînœ are very similar to those of 

 the Opliiodermatidce. In Ophiochiton fastigatus Lyman, the peristomial 

 plates are triple, one of the secondary plates filhng up the outer 

 open angle formed by the other two. The oral frames are very 

 long, with V-shaped grooves for the ambulacral ring canal, as in 

 Ophiarachna incrasscda and Bathijpecihiura gofoi. The genital 



1) In my opinion, Ophiochiton hjmani Sti'der, 1883, does not belong here, and is an 

 Ophiocten, allied to sucli sj^ecies as Ophioden hastatmn Lymax, 1878, and pacificum Lütken & 

 MonTENsEN, 1899. 



