BY T. HARVEY JOHNSTON AND O. W. TIEGS. 131 



Figs. 61-62. Flmhellodiscus simplex. 

 61. Young form; 62. (adult) Transverse section through anterior end. 



Figs. 63-64. Empleuro discus angustus. 

 63. Toothed disc; 64. Posterior disc in actual attachment to gill-filament as 

 viewed from ventral side, through the gill-tissue. 



Plate XX. 



Figs. 65-72; Lepidotes fluviatilis. 

 65 Entire animal; 66- Reproductive organs slightly diagrammatic; 67. Disc. 

 ventral view; 68. Transverse section through head region; 69. Toothed disc; 70. 

 Head of half-grown animal; 71. (adult) Transverse section through region posterior 

 to testis; 72. Young animal (ventral view), 



Plate xxi. 

 Fig. 73. Lepidotes fluviatilis. 

 Transverse section through region of cirrus. 



Figs. 74, 78, 78a. Lamellodiscus typicus. 



74. Disc; 78. Entire animal; 78a. Cirrus. 



Fig-s. 75-77. Calceostoma glandulosum. 



75. Transverse section in regioni of oviduct; 76. Transverse section of skin; 77. 

 To show excretory openings in head region. 



Plate xxii. 



Figs. 79-86. Calceostoma. glandulosum. 



79. Entire animal; 80. Head in side view; 81. Reproductive organs; 82. A 



small portion of the cephalic glands; 83 To show the articulation of the hooks; 



84. Two minute hooks; 85. Hook apparatus of disc; 86. Disc, ventral view. 



