Victorian Fossils, Pari IX. 211 



Tlie genus Ecionema is delined hy SoUas' as '' Jilijilidastrose 

 Stellettidae. in which the ectosome does not form a cortex, 

 with two fiirnis of microscleres, one of them being a microrabd, 

 derived either from an anthaster or a chiaster by reduction 

 in the number of the actines to two." 



In the present specimen there are at least four types of 

 microscleres ; spherasters, sterrasters, microstrongj'les and the 

 microrabds (probably derived from a chiaster). It may sul)se- 

 queutly be found necessary to form a new genus for the 

 reception of this sponge should other specimens occui-, but for 

 the present it may be referred to Ecionema. 



Extended Description. — In addition to the characters noted 

 by McCoy, we may state that the spicules consist both of the 

 large (megalo*cleres) and the small types (microscle'res). The 

 former consist of — (1) long arcuate or sigmoidal spicules pointed 

 at both ends (oxea), generally smooth, sometimes slightly 

 spinose ; and (2) tetraradiate spicules of the form protriaene, 

 with the three short rays directed away from the main axis, 

 sometimes cun'ed, but more often straight, forming an angle of 

 about 45 deg. from the axis of the rhabdus produced. There 

 are also occasional dichotriaene, in which the three radial cladi 

 are bifurcate, and with the main actines suppressed, after the 

 manner of Ecionema nana. Carter sp.- The microscleres con- 

 sist of — (1) arcuate or open V-shaped microrabds, cylindrical 

 and with rounded ends (micro-trongyles), bearing surface tuber- 

 culations and depressions; (2) a Ispiraster, with blunt spines, 

 especially neair one extremity ; (3) a microxea with whorls of 

 spines ; (4) a spheraster. with moderately long arms carrying 

 two or more spines at the exti'eme tips ; (5) a depressed ellip- 

 soidal sterraster. with .'hilum nearly central ; and (6) a sani- 

 (laster slightly tapering to one end. and armed witli numerous 

 short spines. 



Dimensions of the Spicules. — The chief skeletal spicules are 

 the oxea. which are nearly ahvayi? slightly curved : the greatest 

 length they appear to attain is about 5 mm., although McCoy- 

 says " some apparently about 1 inch long."'' They are massed 



1 Loe. supra eit., p. 195. 



2 Annals and Man'. Nat. lUst., ^ii'V. \'., vol. \i., 18>i0, pi. vii., f. 48. 



3 Loc. cit., p. 31. 



