io 



expansions. Buds? Tentacles 8. Stomach without lateral lobes. Stalk from one and a half to 

 twice as long as the calyx, reaching a Iength of 310^., ending in a small disc of attachment, 

 without food-gland. 



The specimens here described were sent to me, in June, 1902, by Prof. C. Ph. Sluiter, 

 who had found them in the course of his examination of Phascolion convestitus, which has been 

 described by him as a new species in the 'Siboga' Report l ) on the Sipunculids and Echiurids 

 obtained by the Expedition. I have the pleasure of naming this species of Loxosoma after 

 its discoveren 



The occurrence of the Loxosoma has already been recorded by Prof. Sluiter in his 

 Report. As there pointed out, the Polyzoon occurred on all the specimens of the Phascolion, 

 principally on the posterior extremity of the body, although a few were found on the anterior 

 end as well. 



Loxosoma has frequently been recorded on the skin of Sipunculids. The best known 

 species is L. phascolosomatum Vogt, usually found on species of Phascolosoma ; differing in man)' 

 respects from the 'Siboga' form, and notably in the great Iength of its stalk. A Loxosoma was 

 recorded by Brumpt ~) from Pliascolion strombi at Roscoff ; but it was neither described nor named. 

 Two species have more recently been described by Nilus 3 ) from Phascolion spitzbergensc found 

 in the Kola Fjord, on the Murman Coast of Barents Sea. Of these, L. murmanicum was found 

 on the anterior end of the Pliascolion, and L. brumpti on its posterior end. The aboral ends 

 of the calyx and the stalk of L. murmanicum are covered by a thick brown cuticle; thus 

 differing from the 'Siboga' species. L. brumpti does not possess this thick cuticle, but bears 

 two projecting organs, believed to be sense-organs, one on either side of the oral end of the 

 calyx. Both the species described by Nilus are said to have 8 tentacles; but it may be noted 

 that in fig. 8, given by that author of L. brumpti, 9 are indicated. L. minutum Osburn 4 ), found 

 on Pliascolion strombi and Phascolosoma cremita in the Woods Hole region, E. coast of N. 

 America, is less than "5 mm. in Iength, and has "about eight" tentacles. The stalk is shorter 

 than the calyx and terminates in a well marked, circular pedal disc. 



I have had some hesitation in giving a new name to the 'Siboga' species, since I have 

 been unable to obtain any evidence with regard to some of its most important features, such 

 as the number of the buds and the character of the gonads. The absence of buds is specially 

 noteworthy, particularly in view of the fact that many of the individuals are small, with a 

 calyx-length of not more than 76 u.. It is possible that they are all young individuals which 

 have been produced by the metamorphosis of larvae. The 'Siboga' species is a very small form, 

 its calyx-length of 150 u. being much smaller than that of L. murmanicum (352 p.), which, 

 moreover, has a very short stalk, or than that of L. brumpti (320 u.), which it more nearly 

 approaches. The number of tentacles (8) is identical with that of both species described by Nilus. 



So far as I have been able to ascertain, there is 110 specific difference between the 



1) Monogr. XXV, 1902, p. 32, 33. 



2) Brumpt, Ë., 1807. Arch. Zool. Exp. (3) V, p. 494. 



3) Nilus, G., 1909, Trudui StPeterb. Obschch. XI, I, N° 4, c. r. Séances, p. 157. 



4) Osburn, R. ('., 1912, Buil. l'.ur. Fisheries (Washington, I>. C). XXX, p. 212. 



10 



