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GENUS MURICELLA, VerriU. 



This genus was established by Verrill (" Trans. Connect. Acad.," vol. i. 

 1S<59, p. 450) for the following species of Miiricea : M. flexiiom, Kolliker ; M. 

 iiitida, Kolliker; M. //nino.^n, Kolliker, and M. tuherriilata, Kolliker. To this 

 list must also be added M. nmhraticokles, Studer, although this form shows 

 affinities to Acis. Since that time the following species have been added : M. 

 tenevn, Ridley ; M. perrainoxa, Ridley ; M. purpurea, Whitelegge ; M. crassa, 

 Wright and Studer ; M. romplanatd, Wright and Studer ; M. gracilis, Wright 

 and Studer; M. Jiexilis, Hiles ; M. r((mosa, Thomson and Henderson ( = iW. 

 ceyloneiixis, Thomson and Henderson) ; M. hen/jah'i/sis, Thomson and Henderson ; 

 M. rubra, Thomson ; M. rubra, Thomson, var. robusta nov. We must now add 

 two more — M. arborea, n. sp., and M. robusta, n. sp. 



The following is an emended diagnosis of the genus : Colony branched 

 mainly in one plane with or without anastomosis ; coenenchyma generally thin, 

 usually with an inner layer of small and an outer discontinuous layer of 

 larger spicules ; the verruca? are short, subconical or wart-like and usually arise 

 at right angles from their bases ; the axis is horny and sometimes chambered, it 

 may be thin and slender or hard and almost inflexible ; the spicules of the 

 ccenenchyma are long warty spindles, shorter forms occur in the verrucpe where 

 they are generally arranged longitudinally in eight bundles with eight project- 

 ing teeth, but sometimes transversely, obliquely or "en chevron " ; the antho- 

 codiae are completely retractile ; the tentacular operculum is usually fairly well 

 developed, consisting of a "crown and points". 



For a classification of the species we find no character or characters so abso- 

 lutely constant as to afford a basis on which groups might be formed, but it may 

 be useful to discuss, in a general way, the chief points of generic importance. 



{a) Branching. — In this connection it is noteworthy that all the species with 

 one exception, viz., M. arborea, n. sp., are branched in one plane ; in the latter 

 the twigs arise in four directions, i.e., in two planes at right angles to one 

 another; in some species, however, e.g., M. complanata, Wright and Studer, 

 small twigs arise from the plane of ramification on one surface, a fact which 

 might probably be explained by a study of habitat. The angle of origin of the 

 branches though not absolutely definite is yet fairly important ; it seems almost 

 constant in certain species, e.g., the angle is (1) acute in M. nitida, Verrill ; (2) 

 about 45° in M. complanata, Wright and Studer; (3) approximately a right angle 

 in M. umbratiroidcs, Studer ; M. gracilis, Wright and Studer ; M. ra/nosa, 

 Thomson and Henderson, and M. arborea, n. sp. In M. rubra, Thomson, the 

 angle of origin varies from 30° to 90° and cannot be relied upon. 



Anastomosis has been recorded for M. umbraticoides, Studer, and M. 



ramosa, Thomson and Henderson, but is not constant even in one species. 

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