239] TURBELLARJA FROM THE MISSISSIPPI BASIN— HIGLEY 45 



About the last of July a few individuals of this species were found in the 

 overflow waters of the Illiaois river. They were in every way more developed 

 than the other specimens seen. The length was over 4mm., the color a glisten- 

 ing milk-white, the intestine rounded and standing out clearly, the whole 

 animal having a weU-fed appearance. The characteristic nervous movement 

 was conspicuous. Under a very small stimulus, excited and almost terrorized 

 actions were aroused. The rather peculiar waves of motion which pass over 

 the body as it hunches along are to be noted in contrast to the smooth maimer 

 of most species. In this instance, the waves were very well marked especially 

 at the anterior end, giving the animal when in motion a ridged or wrinkled 

 surface, quite significant. 



FAMILY DALYELLHDAE 



The Dalyelliidae have had an irregular history. Starting in 1843 with 

 the descriptions of Oersted and continuing to the present time, this family 

 has been the subject of many descriptive and systematic studies. Oersted 

 named several species belonging to the genus Oerstoma and then proposed the 

 family name Derostomeae. Schmidt (1848), Uljanin (1870), and Jensen 

 (1871) worked over this family adding species and defining the genus characters 

 as well as describing several genera belonging to other nearly related families. 

 In 1882 von Graff reclassified the whole group, incorporating with Derostoma 

 the old genus Vortex Ehrenberg (1831) and naming the family Vorticiidae 

 from the latter genus. He created two subfamilies to contain the eight genera. 

 Then, later, in 1903, he again renamed the Vorticiidae, making a family, 

 Dalyelliidae, with two sub-families, the Graffillinae and the Daly elliinae named 

 after the two oldest genera, respectively, and at this time also because Vortex 

 had been used in 1797 for another form, he substituted the name Dalyellia 

 first used by Fleming in 1822 for that genus. Again in 1908 on the basis 

 of a paired ovary he m^ade two families the Graffillidae with two ovaries and 

 the Dalyelliidae with only one. Ihe latter family was made to contain six 

 genera and sixty-one species, all European form.s. Before 1911 three or four 

 species had been identified for this country, all new. In his paper of that 

 year von Graff described eleven others, most of them taken from the locality 

 around Rochester, N. Y. Thus the present conception of the family is quite 

 different from the early orignal description. 



The mxore general distinguishing details are the presence of a single ovary 

 and two yolk glands, a simple genital pore, and the anterior barrel-shaped 

 pharynx without a sheath. 



The pharynx is the m^ost conspicuous detail of structure. It is often slender 

 and long, often short and nearly spherical, but generally the checkered appear- 

 ance of the wall is well-developed. It is always of relatively large size and 

 holds its shape constantly, not being at all collapsible. It is thus very sharply 

 marked off from the intestine which is of very different structure. During 

 the reproductive season the vitelline glands running forward on each side of 



