BpoNeniDA. 625 



TETBAOTINELLIDA. 



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

 family Choristidae is alone represented. The proportion of species 

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

 collection ; but we miss the genera Geodia and Plaeospongia, which 

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

 discoid dermal plates which stands between Geodia and Stelletta is 

 represented by a new species. 



CHOEISTIDiE. 



49. Tetilla dactyloidea. 



Tethya dactyloidea, Carter, Ann. Sf Mag. N. R. 1869, 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 wallichi, Wright, when perfect— i, e. 

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

 but depressed- and agariciform. Its diameter is much greater 

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

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

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

 forked anchor does not exhibit a constant iaequality in the length 

 of the arms. 



Hab. Grlorioso Islands, low water. 



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



ERYLUS, Gray. 



Stelletta, pars, Schmidt, Spong. Adr. Meer., Spong. Kiist. Alg., i^ong. 



Atl. Gek; Carter, Ann. ^ Mag. JST. H. 1880, v. p. 135. 

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

 Discifera, of subsection Pycnodermata of group Stellettina, Carter, 



Ann. if 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. mamiUaris, Schmidt. It may be characterized as : — 

 Comprising Choristid Tefcractinellida with the surface covered by a 

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

 spioule and small steUates with slender and few rays. Form 

 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 the described species Stelletta euastrum, S. 

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

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



2s 



