REPORT ON THE HEXACTINELLIDA. 3r)9 



])()rted by three to five layers of regularly coalescent hcxradiate forms enclosing culjical 

 meshes. Here, too, as in Myliuda grayi and in many fossil sponges, each ray of the 

 liexradiate spicules is united at a certain distance from the node of intersection with one 

 of the four adjoining rays by means of a siliceous bridge passing off at an angle of 45°, 

 so that by means of these the appearance of an octahedral lantern with an internal axinl 

 cross is produced. Marshall, therefore, proposed the expressive name "lantern spicules." 

 As to the oblique bridges between the arms of the central sexradiate spicules, Marshall 

 was able to demonstrate their origin from the fusion of lateral hooks and prickles, which 

 had become apposed to one another. 



Among free spicules Marshall and Meyer found in the interior of the adult tissue 

 scattered rod-like forms slightly bent at one end, and very small hexradiate rosettes, 

 which bear on the extremity of each ray from four to six teeth, arranged like tulip petals. 

 (Jn the other hand, the covering of the soft parts contains on both sides of the tube-walls 

 numerous four-, five-, and six-rayed spicules. On the upper slender margin of the walls of 

 th(^ tubes there was in some places a dense palisade row of smooth uniaxials, which are 

 probably to be explained as a peristomial wreath. The relationship between Myliusia 

 and Cceloptychium was particularly emphasised by JMarshall and Meyer, but this 

 difference was noted, that Cceloptychium is monozoic, Myliusia, on the other hand, 

 polyzoic. 



Oscar Schmidt also found the same species in the West Indian and Mexican region.' 

 He adds to Marshall's description the observation that many nodes of intersection in the 

 dictyonal framework of the specimens examined by him are unperforated. He found, 

 however, a central cavity with which a markedly irregular plexus of externally opening- 

 tubes communicated. The meandering course of these tubes often makes it difticult to 

 distinguish the canals and intercanals. Among the free skeletal elements lie noted 

 " prism rosettes." 



Schmidt regarded Myliusia as a Cystisj)ongia without a covering layer, and provided 

 with conspicuous lantern nodes in the lattice framework. 



To the genus Cystispongia, Roemer, Oscar Schmidt has assigned ;i new living form— 

 Cystisjyongia siiperstes. He has given a careful account of the characteristics of the 

 genus Cystispongia, established by Roemer, and more accurately defined by Zittel, and of 

 the single known species Cystispongia bursa, from the chalk, as also of the living 

 Cystispongia superstes added by him. 



1. Aulocystis grayi (Bowerhank), (PL CIV. fig. 7). 



There is in the British Museum a dried round specimen about 2 cm. in breadth, 

 and 1^ cm. in height, which Gray first described (1859 and 1867) as Myliusia 



' Spongien dea Meerbusens von Mexico, p. 52. 



