spoxgiida. <;_\.» 



TETRACT1NELLIDA. 



As usual with shallow dredgings like thoso of he ' Alert,' the 

 family Choristidue is alone represented. Tho proportion of species 

 to the rest of the collection is about the same as in the Australian 

 collection ; hut we miss tho genera G'< »<tiu and Placospongia, which 

 might have been expected to occur here. The romarkable group with 

 discoid dermal plates which stands between Qeodia and Stelletta is 

 represented by a new species. 



CHOEISTID^E. 



40. Tetilla dactyloidea. 



Tetliva dactyloidea, Carter, Ann. 6f Mag. N. H, 18G9, iii. p. 15, figs. 

 1-5 ; 1872, ix. p. 82, pi. 10. figs. 1-5. 



A somewhat imperfect specimen, having, however, probably had 

 somewhat the form of Thenea ivallichi, Wright, when perfect — i. e. 

 not produced upwards into the long cylinder figured by Mr. Carter, 

 but depressed and agaricii'orm. Its diameter is much greater 

 than that of Carter's specimen, viz. 40 millim. (1| inch); its pre- 

 sent height is 25 millim. (1 inch). Tho spicules agree closely with 

 Mr. Carter's descriptions and figures, with the exception .that the 

 forked anchor does not exhibit a constant inequality in the length 

 of the arms. 



Hah. Glorioso Islands, low water. 



Distribution. S.E. coast of Arabia (Carter). 



ERYLUS, Gray. 



Stelletta, pars, Schmidt, Spang. Adr. Meer., Spang. Kiist. Alg., Spong. 



Atl. Geb. ; Carter, Ann. $f Mag. N. H. 1880, v. p. 135. 

 Erylus aud Triate, Gray, P. Z. S. 1867, p. 549. 

 Discifera, of subsection Pycnodermata of group Stellettina, Carter, 



Ann. $ Mag. N. H. 1883, xi. p. 348. 



I have already indicated (Part I. pp. 471, 472) that the species 

 called by Schmidt Stelletta, but provided with disks composed of 

 modified trichites, should be definitely separated from that genus. 

 I adopt for this distinct group the generic term which Dr. Gray 

 assigned to S. mamillaris, Schmidt. It may be characterized as : — 

 Comprising Choristid Tetractinellida with the surface covered by a 

 layer of detached discoid trichito globates, and having besides a zone- 

 spicule and small stellates with slender and few rays. Eorm 

 lobate. Vents single or multiple. 



It differs from Geodia in the discoid form of the trichite masses 

 and their independence of each other (in Geodia they are united by 

 ligaments). It includes tho described species Stelletta euastrum, S. 

 mamillaris, and S. discophora, Schmidt, and S. euastrum, Carter. 

 Stelletta geodina and S. intermedia, Schmidt, should be referred to 

 Geodia. 



2s 



