10 ART. 9. T. IJIMA : H EX ACTIN ELLIDA. . 



tip of two oppositely standing prongs. The prongs are strong, 

 recurved ; in number 5-8, usually 6, to each disc. Now and then 

 the rosette under consideration takes the form of a discohemi- 

 hexaster (fig. 11), in which one or more of the principals have 

 only one terminal in a straight line while the remaining principals 

 have two in the usual disposition. In a few cases I have observed 

 a uniterminal ray crooked near the base in much the same way 

 as is known to sometimes occur in oxyhemihexasters of certain 

 Possellids. Purely hexactinose form of the discohexaster in ques- 

 tion (=F. E. Schulze's Derivat- Hexactin or Discohexactin, which 

 terms I think had better be avoided as liable to lead to a mis- 

 conception) is also met with, though only very rarely. Such a 

 hexactinose discohexaster exactly corresponds in shape with the 

 same of Corbitella elegans (PL, fig. 13) but is smaller by nearly 

 one-half. 



Possibly a second form of discohexaster, differing considér- 

 ai >ly from the one above described, is to be ascribed to the species. 

 I say this on the strength of the single case I have discovered 

 of the very small, incompletely preserved discohexaster, which I 

 have shown in PL, fig. 12. It measured only 40 ^ in diameter. 

 From each short principal there arise divergingly slender, rough- 

 surfaced terminals, 3 or 4 in number. The terminal disc is 

 composed of about G minute claws forming an irregular umbel ; 

 at any rate the claws are not uniformly recurved and seem to 

 spring at variable angles from the end-point of the terminal. 



The graphiocome has never been observed intact. Neverthe- 

 less, its presence in the species is not to be doubted from the 

 occurrence of fine rhaphides (about 150/^ long), either isolated or 

 grouped into bundles, and which, as I have shown in the last 

 Contribution, take their origin as the terminals of graphiocomes. 



