20 



There is a single polian vessel and but one madreporite. 

 Dependent from the anterior region of the interior of the 

 pharynx are over one hundred digitiform processes, the 

 nature of which is discussed elsewhere. The deposits in the 

 perisome consist of cruciform bodies with spinous processes 

 projecting in a plane perpendicular to their surface (plate iii., 

 fig. l,a,h,c,d). The arms of the cross are in some cases produced 

 so as to form a hole. The spicules give one the impression 

 of being in a developing stage. The species appears to differ 

 from any previously described, but Thyone sacellus, Selenka, 

 would seem to be a near relative. The latter, however, differs 

 in the form of the calcareous ring, and, moreover, the 

 spicules of our present species could not very well, even if 

 they be regarded as not fully developed, proceed to the form 

 of- those found in T. sacellus. 



Thyone, sp. indeterm. 



There is a single specimen of a Thyone, in which cal- 

 careous deposits are completely wanting. Their absence from 

 the perisome would not be regarded as inhibitive of a deter- 

 mination, but as they have in this case disappeared from 

 the tube-feet, where there is some evidence of their having 

 been previously present, we do not care to endeavour to 

 identify the species. 



Thyone nigra, n. sp. 



One specimen collected by Dr. J. C. Verco. 



Description. — Shape fusiform, the posterior and anterior 

 ends being upturned. Podia distributed without arrange- 

 ment all over the body. Tentacles ten, frondose ; the dorsal 

 are about double the length of the ventral. Colour, deep 

 purplish-black, podia white. The calcareous ring consists of 

 ten processes (plate iii., fig. 4), having prolongations pos- 

 teriorly. Calcareous deposits are thickly disposed throughout 

 the perisome; they consist of tables of two kinds (plate iii., 

 fig. 3). The first, which measure about 0'096 mm. x 0*064 

 mm'., are of an irregular oblong shape; the disc is flat, and 

 is pierced with four large central holes. These form a cross. 

 There are other holes, which are irregularly disposed. The 

 spire of the table is very short ; it consists of two rods which 

 ar6 joined only at their extremities, which are spinous. 

 The second kind of table consists of a rhomboidal plate, 

 pierced as in the first - mentioned with four central 

 holes and with a few holes at each extremity. The 

 plate is distinctly concave, the spire is similar to that 

 in the first kind ; these rhomboidal plates occur exclu- 

 sively in the skin of the podia. Internally the anatomy shows 



