MONOGEArH OF JAPANESE OrHIUROIDlvV. " 59 



ed by double rows of liook-bearing granules, so that the arm is 

 annulated by the minute hooks. Lateral and ventral arm plates 

 confined to the ventral side of the arm. More than three arm 

 spines, all ventral in position, serving as tentacle scales. Vertebrae 

 very short and exceedingly stout, discoidal, with typically strepto- 

 spondyhne articulation. Upper muscular fossos of the vertebrae ex- 

 tremely large, the lower very small. This family includes twenty- 

 four genera, which may be grouped into two subfamilies. 



Subfamily 1. Gorgonocephalince mihi, 1915 : — Teeth, dental 

 papillae and oral papill£e all similar, spiniform ; oral angles not 

 strongly projected ventrally ; genital slits small, often pore-like, 

 lying near the disk border ; basal vertebrae not very small, not 

 covered over by the muscles lying between the basal vertebra? and 

 genital plates ; arms simple or divided ; those forms with arms 

 simple or divided a few times have no supplementary plates in 

 the spaces between the oral angles and the interbrachial ventral 

 surfaces, while those with arms divided many times have well 

 developed supplementary plates in the spaces mentioned. 



I. Arms simple or divided a few times ; no supplementary 

 plates in the spaces between the oral angles and the 

 interbrachial ventral surfaces. 

 a. Arms simple. 



Astrogomphiis Lyman, 1869. 

 ' Astrochlamys Kœhlek, 1912. 



Astrochele Veekill,- 1878. 

 Asteroporpa Œested & Lütken, 1856. 

 h. Arms divided a few times. 

 Astrocnida Ly]\ian, 1872. 

 Conocladus Clx\ek, 1909. 

 II. Arms divided many times ; supplementary plates well 



