48 A MONOGRAPH OF THE 



crustular dermis, and are slightly imbedded in its substance, 

 while the attenuato-recnrvo-ternate ones are less regularly 

 disposed. The heads of some of these are intermixed with 

 those of the expando-ternate ones at the inner surface, but 

 a considerable number of them project their triple hooks 

 deep into the substance of the crustular dermis, and occa- 

 sionally almost reach the outer surface. The shaft of this 

 form of spiculum is very slender compared with its length, 

 which is greater than that of the expando-ternate ones, while 

 the diameter is not above one fourth that of the latter; 

 the shaft is also frequently flexnous. Occasionally, but 

 very rarely, we find a specimen of porrecto-ternate spiculum 

 mingled with the recurvo-ternate ones. The fusiformi- 

 acerate spicula of the skeleton are large and strong ; their 

 greatest diameter is not quite so much as that of the 

 expando-ternate ones. The interstitial membranes are very 

 abundant, they are of uniform texture, and, when free from 

 sarcode, very pellucid. The type specimen has the mem- 

 branes abundantly coated with sarcode, amidst which are 

 numerous small, lentiform cells, ^th of an inch in diameter. 

 I did not detect these bodies in a specimen in my pos- 

 session in which the sarcode is not nearly so abundant, 

 probably from its having been cleaned by soaking in fresh 

 water. The attenuato-stellate spicula of the sarcode are 

 abundantly dispersed over the membranes ; they are very 

 variable in size, some not exceeding, from point to point of 

 the rays, ^th of an inch, while others attain an extreme 

 diameter of ^th of an inch ; the radii of the largest of them, 

 beneath a linear power of 660, exhibited a tendency to be 

 incipiently spinous. The gemmules are uniformly globose ; 

 an average sized one measured ^rd of an inch in diameter. 

 I did not observe any of them in a young and productive 

 state in the crustular dermis, but in those which were im- 

 bedded near the centre of the substance of my own specimen 

 there were a considerable number in the young state having 

 the opaque nucleus in the centre. This specimen I obtained 

 from Mr. James de C. Sowerby ; he has no recollection of 

 its history, but says he had various specimens, many years 

 since, from a man who used to collect for Colonel Montagu. 



