1 ;>.-, 



MYZOSTOMIDA. 



BY CHARLES L. BOULENGER, M.A., D.Sc. 



(Zoological Department, University f Birmingham}. 



WITH ONE PLATE. 



I.- INTRODUCTORY. 



Tut'; collection of Mvzostonies brought liack by the "Terra Nova" Expedition is ;i 

 small one. consisting of one free-living specimen and five cysts obtained within the 

 Antarctic Circle at Stations -J94 and 355. 



The only Myzostomida previonslv recorded from Antarctic regions are those 

 collected 1>\- the National Antarctic Expedition (" Discovery "), L 90 1-4, and described 

 by v. Stummer-Traunfels in 11)0$. The "Terra Xova " collection contains represen- 

 tatives of the two species dealt with in this author's report, and includes no forms new 

 to science ; it is, however, not devoid of interest since the cyst-forming specimens 

 lielong to the remarkable species Mi/ci^fniiin i-i/xfifnfn, v. (-Jratf, and four of the five 

 cvsts were obtained from the peculiar Crinoid Promachocrinus kerguelenensis, a form 

 riot previously recorded as the host of Myzostomida. 



In the structure of their cvsts and in their position on the body-disc of the 

 host these parasites differ from all previously known examples: their size, moreover. 

 considerably exceeds that of tlie specimens described l>y v. Stummer-Traunfels and 

 other observers of the species, 



II. SYSTEMATIC. 



IMY/OSTO.MA. F. S. Leuckart. 

 Myzostoma antarcticum, \. Stumm.-Tr. 



Mi/::iiiiiiiiini inihirctn-iiiii. \. Stummer-Traunfels, X.-it. Ant. V\\\\. (' Disc-ovi-ry ''), l'.i01-4, 



vol. \\ , r.MIS. My/."i-t..ini(l:i-, p. 2. 



This species was fonned hv v. Stummer-Traunfels for a imml>er of free-living 

 specimens from ,!////// adriani, Kell. collected liy the " lisco\er\ " Expedition. It is 

 represented in the "Terra Nova" collection l>y a single individual taken at a depth of 



VOL. II. V 



