REPORT ON THE HEXACTINELLIDA. 



Glaus ^ now pronounced against any close systematic union of Euplectella and 

 Hyalonema. 



On the otlier hand, in 1868 Wyville Thomson first recognised the common relation- 

 ship of all Hexactinellida, though he was not able to separate them sufficiently sharply 

 from the Lithistida. The characters of his order Vitrea were given in these words : - — 

 " Sarcode in small quantity, very soft, never containing formed horny matter, either 

 fibrous, membranous or granular. The skeleton consists entirely of siliceous spicules, 

 either separate (in fascicles or scattered) or anastomosing and combined into a continuous 

 siliceous network. The sarcode contains small spicules of a different character from the 

 general spicules of the skeleton, and of complicated forms. The spicules, whether of the 

 skeleton or of the sarcode, may all be referred to the hexradiate stellate type," and in 

 another place (Phil. Trans., 1869, p. 713) : — "In all the known genera all the spicules 

 are modifications of the hexradiate stellate type." 



In the order Vitrea, Wyville Thomson noted {loc. cit., p. 713) the following genera and 

 species : — 



Genus 1. Euplectella, Owen, 



,, 2. Habrodictyon, Wyv. Th., 



,, 3. Aphrocallistes, Gray, 



., 4. Dactylocalyx, Stuchbury, 



5. Farrea, Bowerbank, 



6. Holtenia, Wyv. Thom., 



7. Hyalonema, Gray (in part). 



8. Adrasta (n. gen.), 



Euplectella aspergillum, Owen. 

 Habrodictyon speciosum, Quoy et Gaimard. 

 Habrodictyon corbicula, Valcncienne. 

 Aphrocallistes beatrix, Gray. 

 Aphrocallistes bocagei, Wright. 

 Dactylocalyx pumicea, Stuchbury. 

 Dactyloccdyx subglobosa, Gray. 

 Dactylocalyx prattii, Bowerbank. 

 Dactylocalyx callocyathes, Gray. 

 Dactyloccdyx azorica, Gray. 

 Dactylocalyx{?)torva,D'a.chiissa.mget'M.iche\otti. 

 Farrea occa, Bowerbank. 

 Holtenia carpentcri, Wyville Thomson. 

 Hyalonema sieboldii, Gray. 

 Hyalonema lusitanicum, Gray. 

 Hyalonema loveni, n. sp. 

 Adrasta infundibulum, n. sp. 



If we except the genus Adrasta, which, though named, has remained undescribed, 

 and even undiagnosed, and further, the above-mentioned Hyalunema loveni, which is not 

 sufficiently defined, and finally the doubtful Dactylocalyx torva, Duch. and Mich., 

 there are only two of the above-cited species quoted which are not Hexactinellida, but 

 belong to the Lithistida, namely, Dactylocalyx prattii, Bowerbank, and Dactylocalyx 



1 Uber Euplectella aspergillum, 1868, p. 4. ^ ^„„_ and. May. Nat. Hist, 1868, vol. i. pp. 11-4-132. 



