32 AET. 2. — H. MATSUMOTO : 



tinuation of the true peritoneal cavity is entirely free from Lyman's 

 " peritoneal cavity." Thus, it may clearly be seen that, Eiiryale 

 is similar to Astroceras and Trichaster in having direct communica- 

 tion between the genital burssG and the perihsemal canal, and to 

 the Asteronychinœ in having the generative glands and the peritoneal 

 cavity lying in the disk instead of being confined to the arm 

 bases. 



The Asteroscliematince are similar to the Asteronychinœ in the 

 perihfcmal canal being entirely free from the genital bursse, but 

 differ from them in the genital bursas being free from each other. 

 In Aster oschema japonicum (Kœhlee), the genital plates are long, 

 stout, lie oblique to the arm axis ; and curve abradially in the 

 outer half of their entire length, so as to narrow the ventral 

 interbrachial spaces. The genital scales are very small, directed 

 laterally to support the disk borders, instead of supporting the 

 abradial border of the genital slits. The genital bursas are very 

 spacious, but do not communicate with the periha3mal cavity or 

 with each other. The radial shields are very long, bar-like, com- 

 posed of several secondary plates, so that they are capable of 

 bending like elastic bars. The peristomial plates are very stout, 

 witli notched outer borders, distinctly grooved in the radial line 

 on the dorsal surface. The oral frames are stout, more or less 

 cylindrical, without distinct distal wings. Ludwig's ' first ventral 

 arm plate ' is present at the dorsal outer corner of each oral slit. 

 Oral plates strongly projecting ventrally as well as dorsally, and 

 provided on the adradial sides with low, smooth, pavement-like 

 grains, corresponding to the oral papilloe. The dental plates are 

 in a single piece for each jaw, w^ith a canal between plate and 

 jaw. Teeth very stout, arranged in a single vertical row. Adorai 

 shields entire, very large ; the outer open angle between eacli 



