THE FREE-LIVING FLATWORMS ^TURBELLARTA) 361 



The following is a list of those forms which are not sufficiently well known 

 to be given their proper place in the key. 



Order Rhabdocoelida 

 Section I Hysterophora 

 Family Catenulidae 



Microstomiim philadelphicum Leidy 185 1 

 Microstomum varlahile Leidy 185 1 

 Section II Lecithophora 

 Subsection Liporhynchia 

 Family Typhloplaxidae 



Typhloplanid from Canandaigua Lake, N. Y., von Graff igii 

 Typhloplanid from Irondequoit, N. Y., von Graff 1911 

 Mesostoma patter soni SiUiman 1885 

 Family Dalyellidae 



Dalyellia hilineata (Wood worth) 1896 

 Dalyellia marginatum (Leidy) 1847 

 Derostoma elongatiun Schmarda 1859 

 Subsection Calyptorhynchia 



Rhynchoproholus papillosus Schmarda 1859 



The following Rhabdocoels are of very doubtful position and relationships 



Vortex (?) cavicolens Packard 1883 



Plagiostoma (?) planum Silliman 1885 



Acmostomum crenulatum Schmarda 1859 

 Order Tricladida 



Dendrocoelum sp. Pearl 1903 



A brief description of these doubtful species will serve to promote their re- 

 discovery and further study. Each description is taken from the original 

 account of the species which is also the only record of it yet published. 



Microstomum philadelphicum Leidy 185 1. 



Body linear, slightly attenuated posteriorly; head conoida! with the apex surmounted by 

 a small oval papilla; tail obtusely rounded. Respiratory fovea subhemispherical. placed at 

 the base of the cone of the head. Mouth oval, projectile; esophagus keg-shaped, intestine 

 narrowed, cyUndroid, dilated at the commencement. Colorless, translucent, ciliated, in- 

 creasing by transverse segmentation, always observed in the process of forming two segments. 

 Length 0.9 mm. Found in water of marshes and ditches near Philadelphia. 



Microstomum variable Leidy 185 1. 



Body broad, linear; anteriorly and posteriorly obtusely rounded. Respiratorj- fovea 

 longitudinally oval, lateral. Intestine very broad. Colorless, increasing by twos. Length 

 from 0.3 to I mm. No nematocysts or rhabdites. Found with Microstomum philadelphicum. 

 Also a chain of 4 individuals was collected in algae culture from shore, Charlevi)ix, Mich., by 

 Dr. H. B. Ward. 



Typhloplanid from Lake Canandaigua, N. Y., von GrafT 191 1. 



Length i mm. Anterior end set off from the rest of the body by depressions at the sides, prob- 

 ably sensory pits. Broadest through middle of body which measures about one-fourth the 

 length. Spindle-shaped rhabdites in glands and tracts of anterior end. Pigment is present in 

 the form of large reddish-brown granules which mostly lie lengthwise of the body, stimctimes 

 branched, and enlarged at posterior end. The pigment forms a reticulation between and passes 

 over the irregularly shaped eyes. Eyes twice as far apart as they are distant from the margin of 

 the body. Pigment of eyes the same as that of the body, only much closer compacted so that 

 they are deeper in color. 



The mouth lies in the anterior third of the body. In the uncompressed animal the pharynx 



