Mr. H. J. Carter on the Hexactinellida?. 357 



between the young and the fully developed rosette in the 

 same species, but the size differs with the form of the rosette 

 and in different specimens. The largest I have met with 

 are in a fragment of Euplectella aspergilhim dredged up on 

 board H.M.S. ' Porcupine.' Here the form represented in 

 fig. 11 is 26-6000ths inch in diameter, while in the specimens 

 from the Philippine Islands it hardly exceeds 20-6000ths. 

 The pappiform rosette with straight capitate rays (fig. 8) is 

 the smallest form ; and this averages in its largest size about 

 8-6000ths. 



Subject to such differences in size, it would of course have 

 been impossible for me to draw all the illustrations which I 

 have given upon the same scale j and therefore, to represent 

 their respective peculiarities, they are for the most part all 

 drawn of the same size. 



Let us now proceed to a list of the Hexactinellidse ; and as 

 it would be confusing to add to each species the place where 

 it has originally been described and illustrated in the list 

 itself, this will be given in a " footnote," to which the reader 

 may refer if necessary. Also, for the same reason, the short 

 commentary on the species contained in the list will be given 

 subsequently. 



Hexactinellidse *. 



General character. Spicules developed upon a sexradiate 

 division of the central canal, held together by silicified fibre 

 or amorphous sarcode, forming a reticulated structure whose 

 interspaces are more or less polyhedral. 



Spicules held together by silicified fibre. 



Species massive, excavated, shallow. 



Rosette or flesh-spicule many-rayed ; rays of equal length, 

 straight, capitate, sometimes only pointed (PL XIII. figs. 4 

 &6). 



Dactylocalyx pumiceus, Stutchbury. Barbadoes. (1) 



pumicea, Gray. Malacca. (2) 



IpMteon jjanicea, Valenciennes. Porto Rico. (3) 



* Abbreviations. P. Z. S., ' Proceedings of the Zoological Society of 

 London.' Annals, ' Annals and Magazine of Natural History.' M. M. J., 

 'Monthly Microscopic Journal.' B.M., British Museum. Atlantisch. 

 Spongienf., ' Grundziige einer Spongienfauna des atlantischen Gebietes.' 



1. B.M. 1841, P. Z. S. p. 86 ; and 1869, p. 77, pi. iii. fig. 1, Bk. 



2. B.M. 1867, P. Z. S. p. 506, pi. xxvii. fig. 2, —IpMteon Imjalli, Bk., 

 P. Z. S. 1869, p. 331, pi. xxiii. figs. 1-3. 



3. Mus. Jardin des Plantes, Paris. P. Z. S. 1869, p. 324, pi. xxii. fig. 1 . 



