88 CALYCOSILVA CANTHARELLUS. 



twisted for a greater part of their length is much more irregular. Here, the spines 

 scattered along the length of the end-ray are not uniformly distributed and often 

 restricted to its outer, convex side; they are also unequal in size, some of them 

 attaining a very considerable length. Such end-rays usually have only one ter- 

 minal spine, sometimes 6.5 ^ in length, which is directed obliquely outward. 

 The angle between this terminal spine and the adjoining part of the end-ray 

 usually is rather obtuse and not infrequently becomes 180°. In this case the 

 terminal spine appears as the tip of the end-ray, and the end-ray itself becomes 

 simple, as in the oxyhexasters above described. 



Intermediate forms with somewhat curved but not properly spirally twisted 

 end-rays, connecting the helonychhexasters with the regular onychhexasters, 

 have occasionally been found, but they are exceedingly rare. 



Spicules twisted spirally like the helonychhexasters of C. c. var. helix have 

 repeatedly been noticed in Hexactinellida. 



Oxyhexasters and oxyhexaster-derivates with a reduced number of spirally 

 twisted rays have been found by F. E. Schulze in Holascus stellatus,^ Holascus 

 ridkyi,'^ and Rhabdocalyptus mollis^ and by Ijima in the last named species,* 

 in Hyalascus giganteus^ and in Staurocalyptus pleorhaphides.^ 



Discohexasters with the verticils of end-rays twisted spirally round the 

 continuations of the axis of the main-rays from which they arise, have been 

 found by F. E. Schulze in Hertwigia falcifera,'' Rhabdopedella tintinnus,^ and 

 Saccocalyx pedunculata ^. 



Clavules with branch-rays twisted spirally round the shaft have been 

 found by F. E. Schulze in Farrea convolvulus '° and by jWilson in Farrea occa 

 claviformis ^^. 



The spirally twisted oxyhexasters of Holascus stellatus, Holascus ridleyi, 

 Rhabdocalyptus mollis, Hyalascus giganteus, and Staurocalyptus pleorhaphides 

 are similar to ordinary, not twisted oxyhexasters occurring in the same sponge 

 and more or less connected with them by intermediate forms. The same applies 



' F. E. Schulze. Kept. Voy. ChaUenger, 1887, 21, p. 86, pi. 14, figs. 10-12. 

 2 F. E. Schulze. hoc. cit, p. 90, pi. 17, fig. 7. 

 ' F. E. Schulze. hoc. cit, p. 157, pi. 64, fig.s. 10, 11. 



* I. Ijima. Studies on the Hexactinellida, IV. Journ. Coll, sci. Tokyo, 1904, 18, p. 266, pi. 20, fig. 9. 

 *j/, Ijima. hoc. cit., p, 106, pi. 8, fig. 16 

 « /, Ijim^. hoc. cit., p, 229, pi. 16, fig. 8. 



' F. E. Schulze. Amerikanische Hexactinelliden, 1899, p. 23, taf. 3, fig. 8. 

 » F. E. Schulze. Rapt, Voy. ChaUenger, 1887, 21, p. 108, pi. 12, fig, 8, 



'' F. E. Schulze. Hexactinelliden des Indischen Oceanes. II. Abh. Akad. Berlin, 1895, 1896, p. 55, 

 taf. 5, figs. 4, 9, 10. 



i» F. E. Schulze. AmerikanLsche Hexactinelliden, 1899, p. 72, taf, 16, figs. 1, 2, 

 " H. V. Wilson. Mem. M. C. Z,, 1904, 30, p 59, pi. 7, fig, 3 



