MARIONELLA 1 



(Eurystoma Marion, 1870); 



an emendation, with notes on a new birefringent substance, 

 mariohellin, found in the intestinal cells. 



CONTRIBUTIONS TO A SCIENCE OF NEMATOLOGY XI 

 BY N. A. COBB 



United States Department of Agriculture 



Marionella, 2 nom. nov. 



Eurystoma Marion, Ann. Sci. Nat. Zool. V. 13: 19. 1870. Not Eurystoma 

 Raf. 1818. 



Cuticle and setae. The thin layers of the transparent, colorless cuticle are 

 traversed by transverse striae so exceedingly fine that they are very difficult 

 to see even with highest powers of the microscope. Occasionally oblique striae 

 also are to be seen in the cuticle of the lips, running in the direction of a 

 left-handed screw. There are no lateral wings to the cuticle, and the striae 

 are not altered on the lateral fields. There are no longitudinal striae 

 in the cuticle itself, but the attachments of the somatic muscles give 

 rise to longitudinal markings of a character somewhat resembling true 

 striae. The contour of the body is always plain. 



The cephalic setae, which are one-third to two-thirds as long as the lip- 

 region is wide, are six or ten in number. Even when at first sight there ap- 

 pear to be only six, it is frequently found that in reality there are ten, 

 each of the four submedian setae having a very short and very inconspicuous 

 companion hugging its base. The setae, two lateral and four or eight sub-- 

 median, are usually slightly curved, of medium size to very slender, taper- 

 ing, and somewhat acute, and have innervations that are most clearly visible 

 near their bases; they are of medium stiffness to flexible, and spread out- 

 ward from the lateral surface of the head opposite the apex of the onchium. 

 Occasionally the larger setae can be seen to be about three- jointed. There 

 are no special subcephalic setae. On the anterior portion of the neck in 

 the vicinity of the head there are always to be found a few small, slender 

 setae, one-sixth to one-eighth as long as the corresponding body diameter; 

 these usually project at right angles to the neck or incline forward at an angle 

 of sometimes as much as forty -five degrees. Not infrequently among the 

 cervical setae there is one, a dorsal one, two to three times as far back as 



1 This paper was published in the Journal of the Washington Academy of Sciences, 

 vol. 11, no. 21, pp. 504-509 (issued January 9, 1922). It is reprinted with changed pagina- 

 tion but without change of page content. 



2 The name Eurystoma, applied by Marion in 1870 to a new genus of free living 

 marine nemas discovered by him near Marseilles, France, was preempted, having been 

 applied by Rafinesque in 1818 to a genus of molluscs. Naturally, investigations made 

 during the last half century enable one, at the present time, to emend Marion's original 

 description. Having examined as many more new, and as yet unpublished, species of the 

 genus as have been already published, I venture to make this emendation, based on a 

 study of about twenty-five species, and to propose for the genus the new name Marionella, 

 in commemoration of its original author. 



