52 THE VOYAGE OF H.M.S. CHALLENGER. : 



end. It does not completely traverse the mesoglcea, but leaves free on either side 

 a homogeneous layer, which in its turn is bounded by a stripe reaching to the com- 

 mencement of the oral disc, and carrying the usual hard deposits." 



Sp)henopus arenacens, R. Hertwig. 



Habitat. — Station 187, Torres Strait, Australia, September 9, 1874 ; 6 fathoms. 

 Two specimens. 



Sphenopus marsupialis, Steenstrup. 



Habitat. — (a) Station 188, in the Arafura Sea, September 10, 1874 ; 28 fathoms. 

 One specimen. (6) Station 208, Philippine Islands, January 17, 1875 ; 18 fathoms. 

 One specimen. 



In the Challenger material I have found four further examples of the genus 

 Sphenopus; two of these I have. determined as Sphenopus arenaceus on account of 

 their rusty red tint, and other two as Sphenopus marsupialis, in consequence of the 

 earthy-grey colour and the absence of a stalk. It seems to me, however, desirable that, 

 with an opportunity of more abundant and fresh material, a renewed study should 

 be undertaken to decide whether the received specific characters are variable, and 

 whether all three species should not be united in the single Sphenopus marsupialis. 



APPENDIX TO THE ZOANTHE^. 



Genus Stephanidium, n. gen. 



Among the Zoantheae I include with some reserve a genus which is represented 

 by a single species, and has thus been insufficiently investigated. It differs from the 

 characteristic forms of Zoanthese in the absence of incrustations, and the non-formation 

 of a colony. Both characteristics, however, may be absent in true Zoanthese, e.g. the 

 soft-skinned Zoanthus and the solitary Sphenopidse. Of more importance is the fact that, 

 in spite of careful study, I have not yet been so fortunate as to demonstrate beyond all 

 doubt the decisive characteristic of Zoanthese, namely, the regular distribution of micro- 

 and macro-mesenteries. I consequently omit to give separate diagnoses of the species and 

 genus. 



Stephanidium scliulzii, n. sp. (PI. I. fig. 14; PI. III. figs. 1, 7). 



Habitat. — Station 209, off Zebu, Philippine Islands, January 22, 1875; 95 fathoms. 



Dimensions. — Breadth, L5-2 - 2 mm. ; height, about 1*0 mm. 



Some Actinia? were forwarded to me by Prof. F. E. Schulze, found among the 

 Hexactinellidse entrusted to him for description ; they were mainly small, insufficiently 

 characterised forms, which I did not care to investigate ; but among them occurred five 



