H. A. Baylis 
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(2) Raphidascaris Railliet and Henry, 1915 1 . 
Oesophagus with anterior muscular portion and small posterior ventri- 
culus. From the latter springs a small posterior appendix. No intestinal 
caecum. Interlabia present. Dentigerous ridges absent. 
Hob. —intestine and stomach of fishes. 
Species: 
R. acus (Bloch, 1779) (genotype) from the pike ( Esox ). 
(3) Porrocaecum Railliet and Henry, 1912. (Syn. Terranova Leiper and 
Atkinson, 1914.) 
Oesophagus with anterior muscular portion and posterior ventriculus of 
oblong shape, the latter short in the genotype, but in other species frequently 
long and bent at an angle so as to open into the intestine laterally. An 
intestinal caecum present. No oesophageal appendix. Interlabia present, 
usually small. Dentigerous ridges present. 
Hob. —intestine of birds, marine mammals and fishes. 
Species : 
P. crassum (Deslongchamps, 1824) (genotype) from ducks. 
P. depressum (Zed., 1800) from birds of prey ( Falco , etc.). 
P. ensicaudatum (Zed., 1800) 2 from Turdus, Sturnus. 
P. decipiens (Krabbe, 1878) from seals. 
P. antarcticum (Leiper and Atkinson, 1914) from Mustelus antarcticus, 
and probably also 
P . semiteres (Zed., 1800) 3 from Vanellus, etc. 
P. serpentulus (Rud., 1809) from Ardea sp. 
P. heteroura (Crept, 1829) from Charadrius, etc. 
P. spirale (Zed , 1803) from owls. 
P. pradongum (Duj., 1845) from Colymbus. 
Certain species from fishes, with this type of alimentary canal, mentioned by Dujardin, require 
further investigation. 
(4) Contracaecum Railliet and Henry, 1912. (Syn. Kaihleena Leiper and 
Atkinson, 1914.) 
Oesophagus with reduced posterior ventriculus, giving off a solid posterior 
appendix. An intestinal caecum present. Interlabia present, usually very 
well-developed. Dentigerous ridges absent 4 . 
1 Ward and Magath (1916) have described a new genus, Hysterothylacium (type-species 
H. brachyurum Ward and Magath, from the “black bass”), which is stated to belong to the 
Heterocheilidae and to have the following characters: “Esophagus long, slender, with terminal 
spherical bulb. Intestine with short simple cecum, arising from anterior end of intestine, directed 
posteriad.” The oesophageal bulb is said to contain three teeth. The authors do not make any 
comparison between this form and Raphidascaris, but it appears not unlikely that the two forms 
are related It is important to note, however, that the caecum is said to belong to the intestine 
and not to the oesophagus. Wigdor (1918) has described a second species, //. cayugensis , from Esox 
and Ameiurus, which, from its description, can hardly be distinguished from Raphidascaris acus 
2 In P. ensicaudatum the caecum is very small and almost rudimentary, at least in the 
examples seen. 
3 The single specimen of P. semiteres available for study proved too opaque for the structure 
to be made out with certainty. 
1 Gedoelst’s (1916) statement that dentigerous ridges are present in Contracaecum is ap- 
