Mr. H. J. Carter on the Lithistida?.. 441 



with fine, pointed, long spines, while in D. Bowerbankii they 

 are short, blunt, and slightly inflated at the ends ; again, the 

 acerate spicule in the former is not figured (Bk. Monogr.), while 

 the fine-spined subspiral spicule of D. Masoni seems to be only 

 a variety of the more coarsely formed one in D. Bowerbankii ; 

 and the acerate spicule, being also very sparse in the latter, may 

 have been entirely overlooked in the former. Thus, at the 

 utmost, D. Masoni can only be considered a variety of 

 D. Bowerbankii. The secondarily furcate extremities of the 

 arms of the surface-spicule in Dr. Bowerbank's fig. 7 of 

 D. Boioerbankii (I. c.) at once allies it to similar forms of the 

 spicule in Pachastrella abyssi, Sdt., and points out the com- 

 mencement of the filigree which becomes so elaborately deve- 

 loped as the surface-spicules gradually sink into the general 

 structure of the body. Schmidt's Corallistes typus would, 

 therefore, come in here. 



In Theonella Swinhoei and Dactylocalyx PrattUy the arms 

 of the surface-spicules are not straight but sinuous, and, thus 

 overlapping each other, leave circular interspaces which are 

 filled up with sarcode charged with the flesh-spicules, in the 

 midst of which are the pores. The minute, cylindrical, 

 microspined spicule varies much in form, from an elongated 

 ellipse to that of a horseshoe-shaped, cylindrical, linear spi- 

 cule, being also sometimes contracted in the centre and 

 enlarged towards the extremities. 



In MacAndrewia azorica and Kaliapsis cidaris the arms of 

 the surface-spicule, besides being sinuously branched, are also 

 flattened, and possess a dentate curvilinear margin on both sides, 

 while the branches overlapping each other, as before stated, 

 leave interspaces that are filled with sarcode charged with the 

 rough, microspined, acerate spicule mentioned, in the midst of 

 which are the pores. These minute linear spicules, often 

 slightly inflated in the centre, are arranged around the pores 

 in a radiated manner, so that the pore can be opened or closed by 

 their being raised or the reverse. The structure is well re- 

 presented by Schmidt in Corallistes clavatella (op. cit. pi. iii. 

 fig. 7, b), which appears to be equal to MacAndrewia azorica. 

 I possess fragment-specimens of MacAndrewia azorica which 

 were dredged up on board H.M. S. l Porcupine ' between the 

 Faroe Islands and the north coast of Scotland. Unfortunately 

 the specimen of Kaliapsis cidaris which Dr. Bowerbank found 

 on a portion of Oculina rosea from the South Seas was so 

 small that it was "all "absorbed in the mounting and examina- 

 tion. 



In Corallistes poly discus — better designated tl asteroides " by 

 Schmidt on the slide which he sent to the British Museum. 



