68 PEOCEEDINGS OP THE NATIONAL MUSEUM vol.70 



Choanotaenia ransomi, new species 



54. Scolex ; diameter 0.39 mm., from Larus atricilla. 



55. Optical section of retracted rostellum ; length of hooks 0.39 mm. 



56. Single hook ; length 0.039 mm. 



57. Adult proglottis ; breadth 0.08 mm. 



58. Scolex and portion of strobile ; breadth of scolex 0.36., from Qavia 



immer. 



59. Tip of rostellum ; diameter, exclusive of hooks, 0.07 mm. 



00. Scolex and portion of strobile ; diameter of scolex 0.39 mm., from 



Larus Philadelphia. 

 61. Proglottides ; breadth 0.28 mm. 



Plate 6 



Choanotaenia ransomi (continued) 



Fig. 62. Proglottides ; maximum breadth 0.28 mm., from Oavia immer. 



63. Diagram of female genitalia ; from series of sections of material 



from Larus marinus. 



64. Transverse section of strobile ; greater diameter 0.42 mm. ; a, posterior 



edge of segment which separates from the inner core in the follow- 

 ing section of the series. From Larus argentatus. 



65. Sagittal section of ripe proglottis ; dorso-ventral diameter 0.28 mm. 



66. Ovum, sketched from formalin material; diameter 0.072 mm. 



67. Proglottides, from strobile 2 mm. in front of moniliform segments 



shown in the next figure; breadth 0.74 mm. (see text) ; from Larus 

 Philadelphia. 



68. Ripe proglottis ; length 1 mm. 



Choanotaenia, species, from Larus argentatus 



69. Scolex and anterior part of strobile ; diameter of scolex 0.40 mm. 



70. Hooks ; length 0.105 mm. 



Hymenolepis anceps, new species from Mergus serrator 



71. Scolex ; diameter 0.15 mm. 



72. Hooks from rostellum ; length 0.012 mm. 



73. Proglottides, about 1 mm. from scolex; type of strobile with serrate 



lateral margins, breadth 0.18 mm. 



74. Proglottides about 1 mm., from scolex ; type of strobile with closely 



crowded segments ; breadth 0.26 mm. 



75. Adult proglottis ; breadth 1.77 mm. 



76. Ripe proglottis ; breadth 2.60 mm. 



77. Transverse section of ripe proglottis ; diameters 2.66 by 0.70 mm. 



78. Abnormal proglottides ; breadth 2.50 mm. 



Plate 7 

 Hymenolepis ardeae (Fuhrmann) from Butorides virescens 



Fig. 79. Scolex and portion of strobile ; diameter of sucker 0.084 mm. 



80. Hooks from rostellum ; length 0.035 mm. 



81. Immature proglottides; breadth 0.86 mm. 



