EEPORT ON THE MONAXONIDA. 159 



The most striking difference, however, lies in the external form, and this is very 

 remarkable, for the British specimen, instead of being of erect growth and definitely- 

 branched, is merely a small crust, and according to Bowerbank " does not exceed one 

 and a half line in thickness" {loc. cit., p. 229), while the colour in spirit (in the 

 case of the Challenger specimen very pale) is stated to be very dark brown. 



Zoca%.— Station 75, July 2, 1873; lat. 38° 38' 0" N., long. 28° 28' 30" W.; off 

 the Azores ; depth, 450 fathoms ; bottom, volcanic mud. One specimen. 



Genus Acarnus, Gray. 



1867. Acarnus, Gray, Proc. Zool. Soc. Lond., p. 544. 



Megasclera styli and tylota (? the latter may be absent), and echinating " Grapnel- 

 spicules " (cladotylota), consisting each of a straight shaft with expanded base and a 

 stellate projecting end with recurved teeth ; these are the characteristic spicules of the 

 genus. As microsclera there may be palmate isochelse and toxa.^ 



Acarnus ternatus, Eidley. 



1884. Acar7ms ternatus, Ridley, Zool. CoU. H.M.S. "Alert," Brit. Mus., p. 453, pi. xlii.figs. h, V. 



With this species we identify a single small specimen growing on a stone. It is in 

 very bad condition and contains a great deal of foreign matter, but the characteristic 

 ternate grapnel- spicules are abundant in it. The proportions of the spicules differ some- 

 what from those of the type, the main skeleton stylus being a good deal longer, but there 

 are no sufiicient grounds for separating the two forms specifically. 



Locality. — Papiete Harbour, Tahiti ; depth, 20 fathoms. One specimen. 



Habitat— ^omhixy ? (Coll. Brit. Mus.) ; West Island and Prince of Wales Channel, 

 Torres Strait; and Isle des Neufs, Amu-ante Islands (Ridley, "Alert"); Tahiti 

 (Challenger). 



Genus Echinoclathria, Carter (Pis. XXIX., XXXI.). 



1884. Echinoclathria, Carter, Proc. Acad. Nat. Sci. Philad., 1884, p. 204. 



External form various, sponge made up of a honeycomb-like mass of anastomosmg, 

 flattened trabecular. Skeleton reticulate, horny, with or without spicules in the fibre. 

 Megasclera smooth, either styli or tylota ; smooth echinating styli commonly present. 

 Microsclera may be present in the form of palmate isochel^. 



Mr. Carter has given no diagnosis of the genus. Fortunately, however, in addition 

 1 For further details concerniDg the genus, vide Eidley, ZooL CoU. H.M.S. "Alert," Brit. Mus., 1884, p. 453. 



