NO. 2032. ROTATORIA OF WASHINGTON AND VICINITY— EARRING. 403 



The voluminous mastax incloses the incudate trophi, which are 

 notable for the simpHcity of their structure; they are without any 

 inner teeth, reinforcing ribs or other complexities found in the ma- 

 jority of the species of this family. 



From the mastax a very short oesophagus leads to the large stomach, 

 which is divided by a sUght constriction, the anterior portion showing 

 the same characteristic muscular network as the walls of the mastax. 

 The posterior section is thick-walled, with large cells for absorption 

 of the products of digestion. Two rounded gastric glands open into 

 the anterior portion of the stomach immediately behind the entrance 

 of the esophagus. 



The lateral canals, with eight jflame cells each, lead to the moderate- 

 sized contractile vesicle. The ovary is ribbon-shaped; as far as 

 known, the animal is oviparous, at least nothing has been observed 

 that would indicate the contrary. 



Total length, 520 //; length of body, 395 //; greatest depth, 255 /z; 

 length of foot without toes, 90 /<; toes, 36 //; length of trophi, 70 fi; 

 width, 48 ft. 



Type.—Csit. No. 16524, U.S.N.M. 



This species is interesting in that it seems to retain more of the 

 primitive organization than any other known species of the family. 

 While the trophi are as highly specialized as any, the stomach shows 

 unmistakable evidence of the transition from the Notommata-tjpe, 

 where the principal part of the digestion takes place in the anterior 

 section, to the usual AsplancTina-tjpe, where this has become indis- 

 tinguishable from the esophagus and virtually forms part of it. The 

 dorsal antennae are in nearly the same position as that of Notommata, 

 but still retain the characteristic features of Asplanchnidse; under 

 sufficient magnification they are seen to be distinctly double, the 

 two setigerous pits being about 8 n apart. The well-developed, even 

 though small, retrocerebral organ, the conspicuous foot and the small 

 number of flame cells are all nearer the primitive type than in other 

 members of the family. The animal is excessively transparent, and 

 in its habits, as well as general appearance, resembles far more the 

 Notommatidse than its congener, the predacious and powerful As- 

 planchnopus multiceps (Schrank). 



A few specimens of this species were found in the middle of August, 

 1911, on tide-swept flats at Four-Mile Run, near Washington. They 

 occurred only at a certain stage of the outgoing tide, which seems 

 to indicate that they came from the swampy region above the place 

 where they were actually found. It has not been seen since. 



TESTUDINELLA PARVA (Ternetz). 



Pterodina parva Ternetz, Rot. Umg. Basels, 1892, pp. 20, 42, pi. 3, figs. 21, 22. 

 Pterodina bidentata Ternetz, Rot. Umg. Basels, 1892, pp. 20, 44, pi. 3, fig. 23. 

 Pterodina emarginata Wierzejski, Bull. Acad. Sci. Cracovie (for 1892) 1893, p. 407. 



