REPORT ON THE HEXACTINL'E 23 



in the arrangement of the ectodermal musculature of the disk 

 and tentacles and in the form of the sphincter being possibly ex- 

 plicable on the assumption that the specimens examined by me 

 were all young. I have not had the opportunity of comparing 

 any of the large specimens of this species with fully grown urti- 

 cinas, but it would seem that the irregularities in the siphono- 

 glyphes which occurred in all of the three specimens examined 

 indicate the distinctness of the species, since such irregularities 

 have not been found to occur in Urticina. 



3. Cribrina artemisia (Pickering) 



Synony>iii\ — Actinia artemisia, Pickering in Dana. 

 Cereus artemisia, Milne-Edwards. 

 Evactis artemisia, Verrill. 



Habitat. — The individuals of this species were found at Dis- 

 covery Bay, the same locality from which they were originally 

 described by Dana ('46). They live buried in the sand, the 

 disk being flush with the surface in expansion, and are attached 

 below to valves of shells or more rarely to stones. 



External Forms. — The base is adherent and the column in 

 contraction is club-shaped (Fig. 25). A short distance above the 

 limbus the column suddenly contracts and then gradually en- 

 larges again until above it may equal or exceed the base in 

 diameter. In all three specimens which I had for examination 

 the tentacles and disk were completely hidden and the upper 

 extremity of the column presented an almost flat surface, slightly 

 depressed towards the center. The appearance presented by 

 these specimens little resembles accordingly the figure given by 

 Dana, but it must be remembered that this figure is of an ex- 

 panded individual. Dana describes the column as being en- 

 larged at its middle and contracted more or less above and be- 

 low. It is probable that in the preserved specimens the upper 

 contracted portion is completely involuted, and the enlarged ex- 

 tremity corresponds to the middle enlargement of the expanded 

 form. 



The column in its lower part is horizontally rugose, evi- 

 dently as the result of contraction, and is provided with a 



