TWO NEW SPECIES OF CESTODES. 269 
The principal features in the anatomy of this worm may be 
thus summed up :— 
Linstowia ameive, sp. n. 
Length up to 25 mm.; greatest diameter 15 mm. Rostellum 
absent ; four suckers unarmed. A neck present ; posterior segments 
increased in length, but not longer than wide. Genital pores 
alternate in position, close to anterior margin of segment. Cortical 
layer thick, about the same diameter as medullary layer; longi- 
tudinal muscles in two layers, innermost of small bundles of fibres 
not more than 8 or 10 to a bundle, and often less, outermost layers 
of fibres implanted singly or in twos. Water-vascular tubes lie side 
by side, the smaller dorsal tube being external; there is also a 
network of excretory tubes. The testes lie posteriorly to the ovary and 
vitelline gland, and extend to the dorsal surface, but do not overlap 
female gonads; cirrus-sac moderately large with muscular walls 
opening into genital cloaca in front of vagina, cirrus without 
spines; sperm-duct coiled, without vesicula seminalis. Ovary 
single with lateral wings, lying in front of segment. Vitelline 
gland, not so extensive, lies behind. Vagina without dilated recep- 
taculum seminis. LHggs lie at first partly within scattered cavities 
in the parenchyma and partly between the meshes of the same; later 
no cavities are to be seen and the ova are imbedded singly in the 
parenchyma ; the eggs are surrounded by three shells. 
Hab. Ameiva surinamensis. 
OOCHORISTICA MARMOS.£, sp. 0. 
Of this new species I have been able to examine but a single 
specimen, which was obtained from an American Marsupial, 
Marmosa elegans. The specimen was not all in one piece; but, 
if the pieces were all of one individual, the length is 84 mm. 
Otherwise the length of the largest piece, which included the 
scolex, was 54mm. The greatest breadth of a ripe proglottid is 
slightly under three millimetres. During life the posterior 
segments were extended to a length of rather more than twice 
their width. They were quite retracted by alcohol and became 
shorter than broad. The unarmed head has the usual four 
suckers, which are directed upwards. There is thus nothing 
distinctive in the external characters of this species. ‘The genera- 
tive pores are not visible, except by the section method; for they 
open anteriorly in each proglottid and their orifices are covered 
by an overlap of the proglottid in front. These pores alternate 
irregularly from side to side of the body as in all other species of 
Oochoristica. 
In transverse sections through this tapeworm it may be seen 
that it agrees with Oochoristica, as opposed to Linstowia, in the 
comparative thinness of the cortical layer, which is less in 
diameter than the medullary layer. The muscular layers in the 
cortex have a characteristic arrangement (text-fig. 4, A), which 
