Lower PaldEOzoic Rocks of the South of Scotland. 57 



Order COLLODAI^IA, H^ckel. 



Suborder Beloidea, Heeckel. 



Spumellaria with an imperfect skeleton composed of nume- 

 rous solid needles or spicula, scattered irregularly in the 

 caljmma. (Chall. Eep. pt. i. p. 28.) 



Genus Sph^rozoum, Mejen. 



Beloidea socialia or " Spha^rozoida with branched or radiate 

 spicula of one kind." (Chall. Rep. pt. i. p. 38.) 



SphcBTOZoum jpriscum^ sp. n. (Woodcut, a-f^ 



Under this name I propose to include spicules of various 

 dimensions, mostly with four rays, more rarely with only 

 three. The rays are usually straight, simple, apparently 

 conical, gradually tapering from a common centre to a point. 

 Three of the rays are either in a plane or form a low tripod, 

 and the fourth ray is nearly vertical to the others. There is 

 a close resemblance in form, and approximately in size, of 

 these detached spicules to the spicules of recent species of this 

 genus and of allied genera of tlie same group, as shown in the 

 ' Challenger ' Report, pis. ii. and iv. The spicules are very 

 abundant, for the most part indiscriminately mingled with 

 one another and with the ordinary spherical shells ; some- 

 times several are now situated close together, as if resulting 

 from the disintegration in position of individual Radiolaria. 

 It is very probable that these spicules may represent more 

 than one species, and they are grouped under one name simply 

 for convenience of reference. In form they are very similar 

 to the spicules of Calcisponges ; but there is not the least 

 ground for suspecting that they may have belonged to these 

 organisms, since their condition of preservation is the same as 

 that of the undoubted Radiolarian shells amongst which they 

 occur, and they are associated with other spicules wiiich as 

 regards form have no counterparts amongst sponge-spicules. 



Detached Radiolarian spicules, both three-rayed and other 

 forms, have already been described by Dr. Riist * from the 

 Jurassic Strata of Western Switzerland and from the Neo- 

 comian of Gardenazza, and they are stated to be abundant 

 in all Jurassic Radiolarian-bearing rocks. 



The rays of the spicules range from '04 to "14 millim. in 

 length and from "005 to '015 millim. in thickness. 



* ' Palseontographica,' Bd. xxxi. p. 284, pi. xxxi., Bd. xxxiv. p. 190, 



