54 



IIIROSIII OUSHIMA : 



inner to the larger. With regard to tiiis point I have examined 

 thirty-seven individuals, in all which the arrangement of tentacles, 

 with their well protruded oral parts, could be easily made out. Of 

 them there were found only two individuals which showed a mid- 

 ventral pair of small tentacles of about equal size, standing side by 

 side. One of these individuals was abnormal in that it possessed an 

 extra tentacle, making in all twenty-one tentacles. In all the remain- 

 ing thirty-five specimens, I have invariably found the tentacles re- 

 gularly arranged in a way which differed from the statements of the 

 three authors mentioned above. 



Of the twenty tentacles they possess, ten are large, five medium- 

 sized, and the remaining five small. Each pair of the large tentacles 

 (textfig. I, Dj, Vj, R t and Lj) is interradial in position and alternates 

 with a pair which consists of a medium-sized (D 3 or R 2 ) and a small 

 (Vo or L 2 ) tentacle. Tn the paired lateral radii the small tentacle (V 2 ) 

 stands always ventral to the medium-sized (D 2 ), while in the mid- 

 ventral radius the small one (L 2 ) is situated to the left of a 

 medium-sized (R 2 ). This agrees with ÖSTERGREN's description of his 

 Pseudocucumis mixta [33, P- 135. and 36, p. 3], excepting the fact 

 that in my specimens the five small tentacles form an inner circle to 

 the remaining fifteen. 



As to the position of the anterior notch in each radial segment 

 of the calcareous ring of the species, SEMPER [42, P- 53] remarked 

 that it is situated " auf einer Seite " in each of the paired radial 

 segments, but in the midventral segment so as to divide this into 

 two equal halves. But for my specimens of Ps. africanus I have 

 found ÖSTERGREN's statements as regards the anterior notches in Iiis 

 Ps. mixta [36, p. 5] to hold true in essential points. The anterior 

 end of each radial segment of the calcareous ring is divided by a 

 deep notch, through which the radial canal and nerve pass, into 

 two unequal halves, one broader than the other (textfig. 4). Again, 

 each of the two halves has on its anterior margin a slight incision or 



