GASTROTRICHA 



625 



(4) Dorsal and lateral surface with deap transverse furrows. Posterior 

 region of body narrow and elongated. 



Ichthydium sulcatum Stokes 1887. 



Total length 0.107 to 0.187 mm.; esophagus not more than one-sixth the 

 entire length. The body is unusually soft and flexible. The lateral margins 

 are so flattened that they impart to the body the effect of wings. The pos- 

 terior region is narrow and very much longer than in other species. 



Fig. 966. Posterior region of Ichthydium sulcatum in dorsal aspect. X about 600. 

 (After Stokes.) 



6 (3) Body covered with smooth scales or with rounded papiUae, but without 



spines Lepidoderma Zelinka 1889 . . 7 



Six species described; three reported from North America. 



7 (10) Minute soft scales present 8 



8 (9) Scales shipld-shaped. . . . Lepidoderma squamatum (Dujardin) 1841. 



Length of body from 0.119 to 0.2 mm., of esophagus 0.042 to 0.044 mm.; breadth of anterior 

 region 0.033 mm., of posterior body also 0.033 mm. Large smooth scales near the posterior 

 end seen in profile simulate curved bristles or spines. Scales on body and neclt in seven alter- 

 nating longitudinal rows; on posterior region eight rows present. New Jersey. 



O^cdO 



Fig. 967. Lepidoderma squamatum in dorsal aspect with characteristic dorsal scales of head, neck, and 

 trunk. X 375. (After Zelinka.) 



9 (8) Scales rhombic, pointed. 



Lepidoderma rhomboides (Stokes) 1887. 



Fig. 968. Lepidoderma rhomboides. A, ventral 

 view of head. B, caudal branch. C. portion of the 

 scale pattern. X 3So. (After Stokes.) 



Length 0.295 mm.; breadth of anterior region 

 0.036 mm. Body long, slender. Esophagus 

 short, "not over one-sixth total length." Scales 

 o 00506 mm. long, thickened along the margins. 

 Posterior margin of each scale appears to carry 



a small triangular supplementary scale. Caudal process remarkably long, marked by about 20 

 delicate rings. New Jersey. 



