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



Subfamily 3. Caulophacin.e. 

 Fungiform, with a long cylindrical tubular stalk. 



Genus 1. Caulophacus, n. gen. 



Funo-iform, with a long tube-like stalk. The gastral surface of the body has become 

 convexly arched by eversion. The dermal surface has either remained convex or has 

 become concave by a turning over of the marginal portion. 



Caulophacus latus, u. sp. (PI. XXIV.). 



About halfway between the Cape of Good Hope and the Kerguelen Islands (Station 

 147, lat. 46° 16' S., long. 48° 27' E.), from a depth of 1600 fathoms and Diatom 

 ooze ground, a Hexactinellid was trawled, which exhibited in its external form a marked 

 resemblance to a flat mushroom. The body is a circular disc, 15 '5 cm. in breadth, with a 

 thickened median portion continued downwards l)y means of a conical neck into the 

 rounded hollow stalk. The latter is 5 mm. in thickness, and is bent obliquely to the 

 side in its upper portion, which is alone preserved. While a shallow depression occurs in 

 the middle of the upper surface, the gradually narrowed marginal portion, which finally 

 terminate!? in a narrow smooth border, is bent slightly downwards (PI. XXIV. fig. 1). 

 On making a section at right angles to the surface (PL XXIV. fig. 1), the afferent and 

 efferent canals are clearly recognisable, and they may even be detected through the 

 uninjured dermal and gastral membranes. These canals are disposed at right angles to 

 the bounding surface. The cavity of the tubular stalk, which is 2 mm. in width, is 

 continued upwards into the efferent system of lacunae in the median part of the disc 

 (PL XXIV. fig. 1). 



Since the upper usually slightly convex surface of the body, which exhibits only in 

 the middle a shallow depression, corresponds to the gastral surface, it is only natural that 

 all the chambers of the richly folded chamber layer should have their wide excurrent 

 openings turned towards this convex surface, and their blind sack-like extremities on the 

 other hand directed towards the concave dermal region. Here, too, as in all other cases, 

 the water enters through the dermal membrane, and passes through the sieve-like net- 

 work of the chamber walls in flowing from the outside inwards. 



The principal parenchymalia are moderately strong, simple, regular hexacts, with 

 smooth rays, each of which runs out to a sharp point, and smooth diacts varying in breadth 

 and length, and provided on both sides with a rough rounded terminal portion. Between 

 these there is an abundant though scattered occurrence of small prickly hexacts 

 (0*25 mm. in diameter) with arched and marginally pronged transverse terminal discs 



