360 FRESH-WATER BIOLOGY 



are likely to be transported in tropical or subtropical vegetation and to make their appearance 

 suddenly and in considerable numbers in greenhouses or in moist shady nooks that have been 

 planted with exotic species. Of one form indeed the proper habitat is not known. Walton 

 has worked out a key and synopsis of the few species reported from North America and ad- 

 jacent islands. In modified form this is followed here. Almost no records of the occurrence 

 of these forms on this continent have been published, and their numbers as well as their range 

 are sure to be considerably extended when attention is directed to them. 



105(110) Eyes either absent or numerous; length more than 40 mm. . . 106 



106 (109) Head anteriorly not broader than remainder of body. 



Family Geoplanidae . . 107 



107 (108) Posterior part of head with eyes in two rows; sides margined with 



orange Geoplana nigrofusca (Darwin) 1844. 



Length 50 mm. Found in Mexico; reported also from South America. 



108 (107) Posterior part of head with eyes in one row; sides margined with 



Hght brown Geoplana stolli (von Graff) 1899. 



Length 60 mm. Thus far known only from a single specimen collected in Guatemala. 



109 (106) Head anteriorly broader than the body. . . . Family Bipalidae. 



Only one species Placocephalus kewense (Moseley) 1878. 



Color dorsally yellow or greenish-yellow 

 with five dark violet longitudinal lines. 

 Length 80 to 250 mm. An introduced 

 species found in hot houses. Its original 

 Fig. 640. Placocephalus Kewense. Anterior end. home is unknown 

 X I. (After von Graff.) 



110(105) Eyes two in number; ventral suckers absent; length less than 



30 mm. Ill 



Rarely the eyes are apparently absent but even here they may be demonstrated in sections. 

 Ventral" suckers do occur in the related family Cotyplanidae . Known from Africa and New 

 Zealand. 



111 (114) Eyes small, marginal sense organs present. 



Family Rhynchodemidae . . 112 



112 (113) Color dorsally light brown with two darker longitudinal stripes 



and transverse area at posterior two-thirds of body. 



Rfiynchodemus syhaticus (Leidy) 1851. 

 Length not over 10 mm. Common in places de- 

 scribed by Leidy (1851) in Pennsylvania and redis- 

 covered in Ohio by Walton (1904). Frequents under 

 ^ side of slightly decayed boards, sticks, etc., in com- 

 pany with snails, the young 

 forms of which it closely re- 

 sembles. Range, Eastern 

 United States. 



B 

 Fig. 641. Rhvnchodemus syhaticus. {A) Dorsal view of individual from Philadelphia, Pa. X J- (5) 

 Individual from Newport, R.'l., showing arrangement of esophagus and structure of mtestme. X about 

 5. (After Girard.) 



113 (112) Color dorsally uniformly dark blue. 



Rhynchodemus atrocyaneus Walton 191 2. 

 Length 20 mm. Only two specimens of this form have been reported. Found at Gambler, 

 Ohio, under decayed boards. 

 114(111) Eyes well developed; marginal sense organs absent. 



Amhly plana cocker elli von Graff 1899. 

 Color dorsally bluish-black with light yellow median stripe longitudinally and yellow "neck 

 band." Length 17 mm. Represented only by two known specimens found in Jamaica. 



