DIBOTHRIA FROM YELLOWSTONE NATIONAL PARK. 
77 
EXPLANATION OF PLATE XXIII. 
Fig. 1. Lignla caiostomi ia abdominal cavity of sucker (Catostomns aniens J. &. G. ). 
a, h. Viscera of host. The heart, liver, spleeu, etc., are crowded into a very small space in the 
anterior dorsal part of the body cavity, 
cc. Intestine of host. 
d. Posterior end of Lignla. 
e. Anterior end of Lignla. 
Fig. 2. Anterior end of Lignla. X 3. 
Fig. 3. Median region of body. X 3. 
Fig. 4. Posterior end. X 3. 
Fig. 5. Anterior end of another specimen. X 3. 
Drawings by the author. 
EXPLANATION OF PLATE XXIV. 
Fig 1. Ligula catostomi. Transverse section near anterior end. X 60. 
aa. Bothria. 
hh. Peripheral aquiferous vessels. 
Fig. 2. Transverse section of longitudinal vessels near anterior end. X 300. 
a. Circular fibers with nuclei surrounding one of the marginal canals. 
b. Lumen of aquiferous vessel. 
0 . Calcareous body. 
d. Nuclei in spongy tissue forming lumen of marginal canal. 
Fig. 3. Transveriso section near posterior end of body. X 27. 
aaaa. Peripheral aquiferous vessels. 
hb. Central aquiferous vessels, 
cc. Marginal canals. 
dd. Testes. 
c. Longitudinal muscle layer. 
/. Subcuticular granular layer, which, when highly magnified, shows the beginning vitellaria. 
g. Incipient generative organs. 
Fig 4. One of the nests of nuclei forming a testiculo d of Fig 3. X 750. 
Fig. 5. Longitudinal section through longitudinal muscle layer from median region of the body, en- 
larged about 300 diameters. The section was made parallel to a lateral face. A few nu- 
clei and calcareous bodies are shown. The latticed appearance of the interstitial spaces is 
due to the radial fibers mentioned in the text. 
Fig. 6. Portion of the border of a transverse section from same region as Fig 2. Enlarged about 300 
diameters. 
a. Crrticle. 
b. Plate of peripheral longitudinal muscle layer. 
c. Granular and nuclear protoplasm. 
d. Nuclei of vascirlar layer. 
e. Calcareous bodies. 
ff. Peripheral aquiferous vessels. 
g. Outer portion of inner longitudinal muscle layer. 
Drawings by the author. ^ 
EXPLANATION OP PLATE XXV. 
Fig. 1. Lignla catostomi. Portion of transverse section from same region as Fig. 3 of Plate 4. Enlarged 
about GO diameters. 
a. Cuticle. 
b. Remains of external longitudinal muscle layer, 
cc. Peripheral aquiferous vessels. 
d. Calcareous bodies. 
ee. Longitudinal muscle layer. 
