REPOET ON THE HEXACTINELLIDA. 405 



municates on the one hand with the funnel-shaped gastral cavity, and on the other 

 hand opens laterally to the exterior by numerous radially disposed and occasionally 

 connected tubes. Between the latter there is a toleral:)ly wide intcrcanalicular system, 

 which does not open, however, into the gastral space. The polyhedral dictyonal frame- 

 work, which penetrates and supports the much-folded plate or tube-wall, consists of fii-m 

 beams, which are beset with numerous transverse rows of small conical tubercles, and 

 united in slightly thickened nodes of intersection, beset with broad tubercled warts. On 

 the dermal and gastral surface of the dictyonal framework there are specially thick nodes 

 of intersection, which never exhibit freely projecting spherical bosses, as in most of the 

 other Dictyonina. The loose spicules of the parenchyma are small lank oxyhexacts, 

 further, oxyhexasters with short principal rays and long S-shaped terminals, disposed in 

 perianth-like fashion, and, lastly, discohexasters with short principals, each with a varying 

 number of long S-shaped externally thickened terminals, forming a tuft and l^earing 

 marginally toothed terminal discs. The dermal and gastral skeletons contain pentacts or 

 sword-shaped hexacts with rounded ends, and with a floricome-like discohexaster of the 

 above type, usually attached to the freely projecting radial ray. West Indies ; Little Ki 

 Island, 140 fathoms; Timor, 200 fathoms; St. Thomas, West Indies. 



Genus 5. Aulocystis, n. gen. 



The body consists of an anastomosing system of tubes. The dictyonal framework 

 encloses scjuare meshes, i.e., cubical spaces, and consists of tubercled beams, in which the 

 nodes of intersection exhibit twelve oblique rod-like buttresses, extending between the 

 six intersecting beams, so that the sides of a regular octahedron are represented. The 

 parenchyma contains loose oxyhexasters and discohexasters. Ox}^ientacts occur in the 

 dermal and gastral skeleton. Graphiohexasters are found iDcneath the skin. 



Species 1. Aulocystis grayi, Bowerbank. 



The octahedral edges of the (" perforate ") nodes of intersection in the dictyonal 

 framework are properly not formed of simple, cyUndrical, obliquely disposed buttresses, 

 but the external margins of plates which stretch between the intersecting beams, and are 

 transversely perforated by several round pores of various size. Over the free bounding 

 surface of the whole dictyonal framework these plates are so much developed, especially 

 in the tangential dii-ection, that they form here and there, by fusion, a perforate siliceous 

 membrane. The parenchyma contains numerous discohexasters with short principal rays 

 of different sizes, and with a variable number of terminals; also small isolated oxyhexasters, 

 with graphiohexasters here and there under the skin. Discohexasters, with medium- 



