OXYURIDS OF MILLIPEDS 



421 



int. 



2. MYOLABIA ON A NEMIC PARASITE OF MILLIPEDS 



The front view of the lip region of Thelastoma attenuatum Leidy, a nema 

 from the intestine of the milliped Sporobolus marginatus, gives the impression 

 at first that there is a circlet of 10 "lobes" surrounding the usual three 

 lips. Careful scrutiny shows that two of these ten 

 lobes, the lateral ones, are the external amphids. 

 This leaves 8 other lobes arranged in 4 submedian 

 pairs. 



A similar condition exists on another, and new, 

 species of Thelastoma occurring in the same host, ex- 

 cept that in this new nema the amphidial lobes do not 

 so closely resemble the other 8. Fig. 3. In the new 

 species the first slice behind the lip 

 region discloses the anterior parts of 8 

 muscular fields that extend throughout 

 the body, as may be shown by cross 

 sectioning. Fig. 3. Furthermore, it is 

 quite evident that the 8 labial "lobes" 

 are the external cephalic expression of 

 these 8 longitudinal muscular fields. 



It is therefore very interesting to find 

 that in a second new species of Thelas- 

 toma, belonging to a new subgenus and 

 infesting a different host (namely the 

 milliped Fontaria marginata Say, as 

 found in Virginia, U. S. A., near the " X 175 



District of Columbia) the 8 organs which g^ 4 and Fl ^S f f 

 in Thelastoma attenuatum are rather in- Tkeiasiom 

 conspicuous lobes surrounding the true 

 lips, have entirely displaced the f .i. f / 

 ordinary lips, forming a lip region ' 

 prominently set off by constric- 

 tion, and consisting of 8 prominent 

 subequal contiguous parts folded 

 completely together over the phar- 

 t ynx and constituting lips of a new 



Fig. 3. Measurements, front r - 



view of the lip region and near- SOrt. 

 by cross-sections of Thelastoma 

 (Thelastoma} spicatum n. sp. 



Figs. 4 & 5. This 



F resents, in cross-section, 

 muscular fields. Fig. 5. 



These lips may be called pseudolabia; or, because of 

 their connection with the longitudinal muscular fields of 

 the nema, myolabia. No cephalic papillae have as yet 

 been seen on these myolabia. 



Diagnosis. Thelastoma (Thelastoma) spicatum n. sp. 

 Much like T. attenuatum Leidy, but smaller and with 

 shorter spicate tail and more completely differentiated, 

 though still rather vague, myolabia. Dimensioned as 

 shown in the formula. Fig. 3. Attenuatum and 

 spicatum may occur together in the intestine of the mil- 

 liped, Sporobolus marginatus. 



Diagnosis. Thelastomellum subg. nov. Thelastomas 

 with 8 well-developed myolabia as in Fig. 5. Type 

 species T. myolabiatum n. sp. 



myoiabiatum spec. 



