L20 THE VOYAGE OF H.M.S. CHALLENGER. 



species or whether Epizoanthus papillosus and Epizoanthus cancrisocius are identical with 

 Epizoanthus parasiticus. 



Family Sphenopid^;. 

 Solitary Zoantheas with the posterior end of the body rounded. 



Sphenopus, Steenstrup. 



Sphenopidse with thick wall, the uppermost layers of which are encrusted with sand 

 granules ; with strong mesodermal sphincter. 



Gray, in his system of the Zoanthese (Proc. Zool. Soc, 1867, p. 236), has erected 

 several genera, in which the individual polyps remain solitary, and are either firmly 

 attached to the bottom or stick in the sand by means of the rounded body-end, viz., 

 the genera Isaurus, Pales, Ovinia, and Sphenopus. As no thorough anatomical studies 

 have been made as yet of all these forms, it is doubtful in the meantime whether they 

 ought to be placed among the Zoanthese or not. Sphenopus is the only one of which I can 

 affirm that it belongs to the Zoantheae, as the macrosepta and microsepta are visible in 

 regular order, and the oesophagus has only one oesophageal groove. 



Sjyhenopus arenaceus, n. sp. (PL II. fig. 10, PL XIV. fig. 8). 



The greater part of the wall is encrusted with sand granules, and so transformed iuto 

 a kind of carapace ; tentacles small and pointed, about sixty in number, distributed in two 

 rows ; thirty macrosepta and the same number of microsepta. 



Habitat. — Cape York. (? The title of the label enclosed with the preparation was 

 nearly entirely destroyed by the rough surface of the animal, and could not be exactly 

 made out.) One specimen. 



Dimensions. — Length, 4 - 5 cm. ; breadth, 2*8 cm. 



Colour. — -(Determined from the spirit specimen) brown-red. 



The wall of Sphenop>us arenaceus, a new species, which I erect here from a single 

 specimen among the Challenger material, is encrusted with foreign bodies to a degree which 

 I have never found in any other Zoanthea ; it forms a firm unyielding capsule, in which 

 the soft parts are completely concealed when the animal is strongly contracted. The form 

 of the Sphenopus then becomes irregularly oval, rather smaller at the rounded posterior 

 end of the body than at the anterior. The wall is inverted a little way at the anterior 

 end, though its nature does not undergo any change. 



The surface is regularly rough like shagreen, as the sand granules are nearly all of equal 

 size. The granules force their way so deeply into the wall that only a thin layer of 

 soft tissue remains on the endodermal side ; it is broadest in the front, and becomes nar- 

 rower as it runs backwards, till the wall at the aboral body-pole consists almost entirely of 



