HEXACTINELLIDS 



WITH 



DISCOCTASTERS. 



49 



Discoctasters with 3-6 straight or almost straight, minutely rough 

 terminals on each principal. Length of entire rays (measured from 

 centre) 53-1 30/i ; those found in deep parts heing often twice as large as 

 those lying near the dermal layer. In larger discoctasters the principals 

 are also rough-surfaced and the terminal discs 7-8 toothed. 



Oxyhexasters 45-76,« in radius. Principals exceedingly short or 

 almost entirely absent. Terminals rough, straight, stout ; usually two 

 to each principal, but Very frequently reduced to one, so that there 

 occur oxyhexasters with 11, 10, 9, 8. 7 or even 6 points. In the last 

 case they may be typically hexactin-shaped though only in external 

 appearance. The principal is rarely supplied with three terminals. 



Microdiscohexasters of usual shape are of frequent occurrence es- 

 pecially in the dermal and gastral membranes. 



Autodermalia are predominatingly rough stauractins forming a fine 

 lattice-work with quadrate meshes. This layer is supported by rather 

 thin strands of hypodermal diactins, forming a network of triaugular, 

 trapezoidal, or irregular meshes, whose sides rarely exceed 2 mm. in 

 length. 



Autogastralia are mainly rough pentactins. These do not form by 

 themselves a continuous autogastral lattice-work but are found scattered 

 on hypogastral strands together with discoctasters and oxyhexasters. 



This species, known only from Sagami Sea, is one of the most 

 abundant Hexactinellids of that locality in depths of over 200 fathoms. 



Genus RHABDOCALYPTUS. 



Discoctasterophorous Rossellids with pentactin 

 hypoder malia, the p a r a t a n g e u t i a 1 rays of which are, 

 when fully developed, armed with hi serially arranged 

 h o o k - 1 i k e prongs. 



When F. E. Schulze instituted this genus for the first time in 

 the Challenger Report, two species were described by him, viz. Rh. 

 mollis and Rh. Roeperi. Later L. M. Lambe* described a third species, 



* Trans. Koy. Soc. Canada. Sect. IV, 1893. p. 37. 



