22 



the mandible, which is of about the. same size as the receptacle, or about half the length of 

 the avicularium is in the form of a crescent. 



The avicularia in the F. abyssicola are still larger than in any of these species, being 

 Vs Va longer than the cells, to which they are also similar in form, excepting that their 

 proximal end is pointed, and the receptacle thus triangular. Lastly the mandible is much larger 

 than in those species, namely of the length and breadth of the cells and of an entirely pe- 

 culiar form, not like a half moon but like a spoon. The only form resembling that here 

 described which I have been able to find noticed by the authors with whom I am acquainted 

 as having written on the subject of Polyzoa, is one described and delineated by Busk under 

 the name of Eschara Platalea (Catalogue of the Polyzoa in the British Museum p. 90, tab. 105 

 fig. 1 3). It resembles a spoon with a short narrower handle, but is without any such thick- 

 ened chitinous lancet-shaped middle-plate as is found in our Flustra abyssicola, representing 

 the body of the proper mandible which has here, while the avicularium is still an organ 

 co-ordinate with the cells of the colony already assumed a strongly elongated triangular form, 

 and also in its whole length is somewhat curved. 



The question as to the proper significance of the avicularia seems, in the preseiit 

 species more than in any other to find its solution. They shew themselves here most evi- 

 dently homologous with the individual animals themselves (the cell and the Polypide therein 

 contained) they are only modifications or reconstructions of the same, destined chiefly for 

 the defence of the colony, and perhaps also in some degree for its support, by retaining the 

 animals of which the more or less decomposed parts may serve as food for the individual 

 members (the Polypides). 



The Flustra abyssicola is evidently one of the oldest now living forms of Polyzoa, 

 which seems like the Rhabdopleura to be much spread in the great depths of the Ocean. 



The new species may be recognised by the following diagnosis. 



Flustra abyssicola. M. Sars. 



Colonia in stirpis formam frondosa fusco-cinerea, subpellucida, rigida, radicata, parce, 

 ramosa, ramis truncatis. Zoooecia utramque paginam stirpis tegentia, elongato-linguiforma 

 setis carentia. Avicularia longitudinem zoooeciorum superantia, eorumque formam referentia 

 sed inferne acuminata, inde receptaculum triangulare; mandibula magnitudinem zoooeciorum 

 aequans, cochleariformis, e parte media longitudinal! dura crassiore lanceolata (mandibula 

 propria) marginibus fusco-luteis et utrinque parte lateral! membranacea tenuissima molli con- 

 stans. Oooecia desunt. Animalia hyalina ore tentaculis 24 cincto. 



Habitat rarior ad insulas Lofoten profunditate 120 300 orgy arum. 



