140 Mr. H. J. Carter on 



radiates small on the surface, where thej are mixed up with the 

 mortar-spicules &c., and scanty on the cloaca, where in their 

 triradiate portions they accord in size and form with the 

 sagittal triradiates of the latter, but with the addition of the 

 fourth arm, which is comparatively short and scantily cchi- 

 nates the interior of the cavity. With reference to that 

 peculiar form of triradiates, whose position has before been 

 stated, and which is of so much paleeontological interest here, 

 it may- be observed that it is two-pronged fork-like, in which 

 two of the arms are projected forwards parallel to each other 

 and closely approximated, while tlie third or shaft is pro- 

 longed backwards in the opposite direction, altogether resem- 

 bling a " tuning-fork,^' in which the arms are smooth, round, 

 and pointed, about 60 by 1 -6000th in. in their greatest dimen- 

 sions, with one arm a little longer than the other, while the 

 shaft, which may be a little longer and double the thickness, 

 is smooth, round, and also pointed, about 75 by 2-6000ths. 

 In their natural position they lie parallel to each other, with 

 their shafts outwards and their forks directed towards the 

 cloaca in bundles " at intervals," as before stated, while it 

 should be added that there are no other spicules in the skeletal 

 structure of the wall but the large long acerates and these 

 crossing bundles, hence the clathrous structure of the simple 

 sarcode becomes very evident, simulating that of the genus 

 Heterojna rather than that of a Le«/conja, which, on thecontrary, 

 is charged with radiates throughout and thus thickened. 

 They are also to be found among the peristome-spicules to- 

 wards their lower part. Size of specimen | in. higli by ^ in. 

 in diameter horizontally ; breadth of head transversely about 



Ohs. It is impossible to compare the above description with 

 that of Hackel's Leucortis indvinar (' Kalkschwanime,' vol. ii. 

 pp. 164-166) without seeing that the two are closely allied, 

 and that, but for the absence of the quadriradiate, the minute 

 acerates or " mortar-spicules," and the peristome in his illus- 

 trations (Taf. 29), one would have been inclined to say it 

 was the same. The " peristome-spicule,'^ however, is men- 

 tioned in the description, but the shape of the large thick 

 body-acerates being sinuous {cf. illustrations), instead of 

 simply curved, is not the same ; so that altogether it is neces- 

 sary to give our species a diiferent designation ; and as this 

 has been done by Dr. Gray both generically and specifically 

 for the original two-pronged fork-like spicules figured by 

 Dr. Bowerbank, Avhich also came from tS.W. Australia, as 

 noticed in my preliminary remarks (/. c), we may fairly 

 assume that they came from this species, and so I have 



