REPORT ON THE HEXACTINI^ 29 



somewhat irregular in shape and were distributed over the en- 

 tire surface of the column, those towards both the margin and 

 the limbus being, however, smaller than those situated in the 

 intervening region. In others again they became obsolete above, 

 occurring on only the lower two-thirds or three-quarters of the 

 column and in one specimen they occurred only on the lower 

 half of the body, those at the limbus in this case being rel- 

 atively very small, while those above were larger, about i mm. 

 in diameter, but were more scattered, that is to say were 

 separated from one another by larger intervals than usual. In 

 the arenicolous specimens again the verrucse were limited to the 

 upper third of the column, not extending upwards, however,, 

 quite as far as the margin, and the lower portion of the body 

 presented no signs of them, except very faint indications im- 

 mediately above the limbus. A further peculiarity of these 

 forms was that numerous particles of sand and shell were ad- 

 herent to the verrucose region of the column, a condition not 

 presented by any other specimens in the collections. 



I have not access at present to all the Hterature dealing with 

 this species, but it seems evident that there is considerable vari- 

 ation in the distribution, size and number of the verrucae in dif- 

 ferent individuals. As regards their distribution the verrucae 

 may present the various conditions described above, or may be 

 apparently entirely absent. To a certain extent at least these 

 variations as seen in preserved specimens may be due to the re- 

 tractibility of the verrucae, which, to quote the statement of 

 Teale ('37) " admit of retractibility to such a degree as to ren- 

 der the corium perfectly smooth, so that the small opaque spot 

 alone indicates their former situation ; they also can be protruded 

 to nearly a line in length, when they bear a close resemblance to 

 rudimentary tentacula. The eminences on one side are often 

 seen in the utmost degree of protrusion, whilst, on the other, 

 they are scarcely perceptible." In some of the present speci- 

 mens, ''the small opaque spots" mentioned by Teale and due 

 to the peculiar structure of the epithelium of the summits of the 

 verrucae, could be perceived on those portions of the column 

 which appeared to be destitute of verruca, but this was not the 



