45 



length still more variable than the basal rays. Frequently it is as long as the 

 basal rays, usually ho-wever it is considerably shorter, and sometimes reduced to 

 a simple, spined and distinctly pointed tubercle. Between these pentactines, 

 and lying in the same level, numerous irregularly-scattered stauractines are met 

 with, which are exactly similar to the basal crosses of the pentactines above 

 described. They are, doubtless, dei'ived from such pentactines by a complete 

 atrophy of the fifth ray. Sometimes one of the four rays is considerably shorter 

 and terminally inflated ; sometimes two opposite rays are atrophied ; and some- 

 times spicules of this kind are met with in whicli only the inflated centre and a 

 single ray are left. 



A peculiar sjiicule is a simple, straight, spindle-shaped oxydiactine 80-1(30 i^ 

 long, which is most frequent in the dermal reticulation and the walls of the in- 

 cuiTent and excurrent cavities, but also occurs in varying numbers in all other 

 jjarts of the sponge. The cylindrical or slightly spindle-shaped central part of 

 this spicule is quite smooth, the pointed terminal conical parts are covered with 

 oblique protuberances and spines pointing outward (pi. VIII, f. 14-16). In 

 Semperella schuUzei such diactines also occur, but here they are spined throughout. 



The second specimen, 12 cm. in length, which is, as stated, somewhat ma- 

 cerated, is in its external shape, general structure and the shape and arrange- 

 ment of the spicules, on the whole so similar to the one described above that I 

 consider it as a young specimen of the same species. There are however some 

 slight differences. The macroscleres for instance are considerably smaller, but 

 this is merely to be ascribed to the youth of the individual, since it is well known 

 that in Hexactinellida generally these spicules increase in size with the age of 

 the sponge. The small parenchymal amphioxes (diactines) are not always 

 smooth in the centre as in the large specimen above described, but are very often 

 spined throughout, as in Semperella schidtzeL One also not unfrequently observes 

 that one end of these spicules is more slender and less spiny than the other. 



Of more importance than these insignificant differences is the fact that in 

 this specimen, by no means rarely mesainphidises occur together with the macr- 

 and micramphidiscs. These mesamphidiscs are 80-100 /* long and on the whole 

 similar to the macramphidiscs. Like them they have 8 spade-like marginal teeth 

 on the margins of their terminal discs, and a knotty or tuberculous shaft. The 

 curvature of the terminal discs differs however, being more regularly hemispher- 

 ical than in the macramphidiscs. 



Although the third specimen is only a small fragment, there can be no doubt 

 about its being specifically identical with the two specimens described above. 

 For not only is that part of the sponge-body and root-tuft which is preserved, 

 similar to the other two specimens, particularly the large one, in appearance and 

 structure, but also the spicules agree perfectly in shape, size and arrangement 

 with those of the latter. I even succeeded in finding in it a few of those 



