CKL'HViJKA. 171 



II., IV., &c), and also off Trincomalee (Stns. XX., XXII), and off GaUe (Stns. XXXIX., 

 XLIL, and XLIIL). 



The Ceylon collection also contains specimens of the corals Heterocyathus mquicostatus, 

 Ed. and H., and Stephanoseris rousseaul, Ed. and H., showing perforations obviously 

 made by burrowing Gephyrea. 



Aspidosiphon spiralis, Sluiter. 



Three specimens of this interesting species described by Sluiter, from the Siboga 

 Expedition were found living in the shell of three species of Murex, M. fuse* 1 *, 

 M. haustellum, and M. tenuispina. The species is interesting because it resembles 

 Phascolion in" living in Mollusc shells, and because in the slight development of the 

 posterior shield, and in the absence of a sharp line of division between the shields and 

 the general surface of the body, it resembles Physcosoma. 



The body is highly adapted to its home. Coiled spirally, it closely follows the 

 contours of the Murex shell. The stout, tough circular anterior shield, on which the 

 introvert opens excentrically but not quite at the edge, forms an effective guard to the 

 entrance of the shell. This shield is supported by a stout, very muscular part of the 

 body-wall which extends for some tenth or twelfth of the total body-length ; after this 

 the skin becomes extremely thin and transparent. In two of the specimens collected 

 by Professor Herdman the anterior shields were deep black, in the third it had a 

 pinkish hue. 



Between the Gephyrean and the Mollusc shell was a packing of sand held together 

 by some secretion. This had a permanent opening at the mouth of the shell through 

 which the introvert could be protruded. 



Aspidosiphon steenstrupii, Diesing. 



A single specimen, probably a young one, as the calcareous deposit was not visible. 

 The musculature agreed, however, with that of this species, and differed clearly from 

 that of A. truncatus. A. steenstrupii is the commonest Aspidosiphon in the Indian 

 Ocean. The specimen in question was taken at East Cheval Paar, in the Gulf of 

 Manaar, from a cavity in a block of coral. 



Centrosiphon herdmani, n. g. et sp. Plate 1., figs. 4-10. 



The length of the two specimens, taken at Cheval Paar, Gulf of Manaar, from the 

 oral shield to the posterior end was 3 centims. The diameter of the oral shield was 

 3 rnillims., of the posterior shield 2"5 millims. The body between these shields was 

 of rather smaller diameter, and from each shield the skin seemed gradually to grow 

 thinner as it passed towards the centre of the body. 



The colour in the spirit specimens was in the main a yellowish-gray; with tinges of 



z 2 



