A NEW MYZOSTOMA, PARASITIC IN A 

 STARFISH. 



WILLIAM MORTON WHEELER. 



Mr. Walter K. Fisher, editor of The Condor, recently sent me 

 a Myzostoma which he took from the ccelomic cavity of a new 

 species of starfish, Tosia (Pentagonaster) leptoceramus Fisher, 

 from Station 4427 off the coast of southern California. The 

 starfish is an extremely flat species and the myzostome was situ- 

 ated in one of the interradial areas, near the gonad, where the 

 body of the host was only 1.5 mm. thick. The parasite ap- 

 peared to be loosely fastened to the ccelomic epithelium by one 

 end and was greatly flattened, in adaptation to the narrow body- 

 cavity of the starfish. 



Comparison of the specimen with the descriptions of the only 

 other known starfish Myzostoma (M. astcricE} shows so many dif- 

 ferences that I do not hesitate to regard the Californian species as 

 distinct. M. asteria:, originally described by von Marenzeller, 1 

 occurs in an hypertrophied portion of the digestive tract in the 

 base of one of the arms of certain small starfishes (Asterias 

 richardi E. Perr. and Stolasterias neglecta E. Perr.) that have 

 been dredged from a depth of 160-710 meters in the eastern 

 Mediterranean. 2 A very careful anatomical and histological study 

 of this species has been recently published by von Stummer- 

 Traunfels 3 so that it is an easy matter to compare the Californian 

 with the Mediterranean species. 



MVZOSTO.MA FISHERI Sp. nOV. 



The specimen is white. It resembles J7. asteria in size and form, being 

 elliptical and broader than long. It measures 6 mm. in length and 8. 5 



^"Myzostoma asferiiz n. sp., ein Endoparasit von Asterias-Arten," Anzeig. k. 

 A kail. iy/ss. IVien., No. 1 8, Juli, 1895. 



2 von Marenzeller, E. " Berichte der Kommission fur Tiefseeforschungen. XVI., 

 Zoolog. Ergebnisse. V. Echinodermen," Denkschr. d. math, naturw. A7. d. k. 

 Akad. IViss. IVien., 62 Bd., 1895, pp. 123-148, I Taf. 



3 " Beitrage zur Anatomic und Histologie der Myzostomen : I. Myzostoma asterias 

 Marenz." Arb. a. d. Zool. last, zn Graz, 6. Bd., No. 8, 1903, pp. 263-363, Taf. 

 34-38. 



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