Division I. Platyelmia

This section includes those Scole-cida which possess a more or less flattened body, usually somewhat ovate in shape, and not exhibiting anything like distinct segmentation. The division includes two parasitic orders - the Taeniada and the Trematoda, - and one non-parasitic order - viz., the Turbellaria. A sub-order, however, of this last, the Nemertidae, does not conform to the above definition; but their other characters are such as to forbid their separation.