70 PKOCEEDINGS OF THE NATIONAL MUSEUM vol.70 



Plate 9 



Hymenolepis macracanthos (continued) 



Fig. 113. Section of cirrus-pouch and vagina, from transverse section of proglot- 

 tis ; camera lucida drawing, Spencer 6/4 mm. s. spliincter muscle 

 of vagina. 



Hymenolepis hamulacanthos, new species, from Marila americana 



114. Scolex ; diameter 0.26 mm. 



115. Rostellum, liooks retracted ; length of hook 0.108 mm. 



116. Single hook; length 0.108 mm. 



117. Mature proglottis, somewhat diagrammatic ; from whole mount, but 



part of vas deferens, vasa efferentia, and vitelline gland supplied 

 from sections; breadth 1.47 mm. 



118. Ripe proglottis, about 20 mm. from posterior end of strobile ; breadth 



1.47 mm. 



119. Ripe proglottis, near posterior end of strobile ; breadth 2.80 mm. 



120. Nearly transverse section of proglottis ; longer diameter 1.62 mm. 



121. Cirrus ; camera lucida drawing. Spencer 6/4 mm. 



122. Transverse section of cirrus and vagina, 0.05 mm. from lateral margin 



of proglottis ; diameter of cirrus 0.016 mm. 



123. Same, 0.09 mm. from lateral margin of proglottis ; same magnification 



as Fig. 122. 



124. Same. 0.21 mm. from lateral margin of proglottis ; diameter of cirrus- 



pouch 0.09 mm. 



125. Transverse section of cirrus-pouch and vagina, 0.30 mm. from the 



lateral margin of the proglottis ; diameter of cirrus-pouch 0.09 mm. 



126. Transverse section of longitudinal muscles; Spencer 10/4 mm. 



Plate 10 



Hymenolepis pachycephala {Llnstom) 



Figs. 127, 128, 129. Scoleces and portions of strobiles; diameters of scoleces 

 0.24, 0.22, and 0.24 mm. 



130. Hooks from rostellum ; length 0.045 mm. 



Hymenolepis podicipina (Szymanski) from Colymbus auritus 



131. Scolex ; diameter 0.17 mm. 



132. Front view of scolex ; diameter 0.17 mm. 



133. Front view of rostellum ; diameter 0.07 mm. 



134. Hooks ; length 0.03 mm. 



135. Immature proglottides ; breadth 0.22 mm. 



136. Posterior end of strobile ; maximum breadth 0.28 mm. 



137. Cirrus ; length of proglottis 0.045 mm. 



138. Transverse section of proglottis ; longer diameter 0.50 mm. 



Hymenolepis rostellata (Abilgaard) from Gavia immer 



139. Scolex ; diameter 0.34 mm. 



140. Tip of rostellum ; diameter, exclusive of hooks, 0.093 mm. 



141. Adult proglottis; breadth 0.68 mm. 



142. Genital cloaca and base of cirrus, from transverse section of pro- 



glottis ; diameter of genital cloaca 0.066 mm. 



