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



extremities and give support to the dermal membrane. The dermal memljrane is 

 strengthened by a very irregular "dermal reticulation" composed of loose spiculo-fibre. 



Sjncules. — Megasdera (PL XL. fig. 9); (1) very long, slender, slightly curved, fusi- 

 form oxea; sharply and rather suddenly pointed; size variable, up to about 1"7 by 0"02 

 mm. (2) Large, usually slightly curved styli, with evenly rounded base ; shorter and 

 stouter than the oxea; size variable, up to about 1'47 by 0'028 mm. The styli are 

 plentiful, Ijut not so common as the oxea ; occasionally also a stout strongylote spicule is 

 seen, evenly rounded off at each end ; these are, at any rate commonly, shorter than 

 either oxea or styli. The full-grown spicule appears to gain in thickness what it 

 loses in length, and this is probably the case in many species, as held by Carter.^ 



Unfortunately all the specimens of this sponge, which seems to be abundant at 

 Station 320, are much frayed out and injured. It is an interesting species which might 

 easily be mistaken for a Eenierine, but the variety in form of the spicules and the 

 arrangement of the skeleton show its Axinellid relationships. It is at once distinguished 

 both from Ciocaly23ta peniciUns, Bowerbank, and Ciocalypta hyalodevma, nobis, by 

 its external form and also by its spiculation. The manner in which the dermal membrane 

 is supported at a distance from the body of the sponge, on the outspread ends of columns 

 of spiculo-fibre, necessitates the reference of this species to the genus Ciocalyjita. 



Locality.— Station 320, February 14, 1876; lat. 37° 17' S., long. 53° 52' W.; off 

 the mouth of the Eio de la Plata; bottom, green sand; bottom temperature, 37°"2. 

 Five or six specimens. 



Genus Acanthella, Schmidt (PL XXXII.). 



1862. Acanthella, Schmidt, Spongien d. Adriat. Meeres, p. 64. 



1870. (?) Pandaros, Duchassaing de Fonbressin and Michelotti, Spong. Mer Caraibe, p. 88. 



Axinellidse of ramose, bushy, or frondose external form ; of cartilaginous consistency, and 

 with glabrous surface beset with ridges and spines ; there is no distinct horny fibre ; smooth 

 linear megasclera {e.g. , styli, strongyla and unequal-ended oxea) are present. No microsclera. 



Schmidt's diagnosis runs " Halichondrise ramosae et fruticosaj, tanquam spinis obsitas. 

 Cutis Isevis, porosissima, qu« in ramis crassioribus sola pigmento infecta est et verte pellis 

 iustar a parenchymate distinguitur. Parenchyma spisse implctum spiculis simplicibus 

 longioribus, substantia firmiori non inclusis." 



The genus appears to us to be a good one, although ([ueried by Vosmaer/ and 

 sufficiently distinct from other genera of Axinellidse to deserve separation ; the original 

 t}^e laAcanthella acuta, Schmidt. 



The cartilaginous consistency is a marked characteristic of the genus, and is evidently 

 due to the peculiar character of the mesoderm. 



' Ann. and Mag. Nat. Hist, ser. 5, vul. iii. p. 284. 



* Broiin's Klass. u. Ordii. il. Thierreichs, Porifera, p. 344. 



