Mesostephcmus appendiculatus — -Martin 
DISCUSSION 
The body dimensions of the adult M. appen- 
diculatus described in this paper are smaller 
than those listed for the species by Dubois 
(1938). This may be due to the fact that the 
duration of the infection was only 9 days so 
that the worms probably had not attained their 
full size even though they were sexually mature. 
The range of egg size and the number of eggs 
( 1-7 ) in the uterus were greater in my speci- 
mens that in those listed by Dubois (1938), 
which include measurements given by Ciurea 
(1916) and Prendel (1930). The anterior ex- 
tent of the cirrus was greater in some speci- 
mens than is shown in Figure 1. The extent of 
the cirrus in Figure 1 resembles that of M. 
microbursa Caballero, Grocott, and Zerecero 
(1954), recovered from the intestines of peli- 
cans, Pelecanus occidentalis calif ornicus, col- 
lected in Panama and in the Coronado Islands 
off Mexico. However, the sucker ratio, spina- 
tion, and extent of the posterior appendix are 
different in the two species. 
The present work extends the range of M. 
appendiculatus to the west coast of the United 
States. It has been found on the east coast of 
this country by Price (1928), in Rumania by 
Ciurea (1916), and in the Ukraine by Prendel 
(1930). 
Dubois (1953) states that pelicans are the 
natural hosts of this species. Since this parasite 
can develop also in dogs, cats, and chicks, the 
present author believes that other fish-eating 
birds probably serve as additional natural hosts. 
Maxon and Pequegnat (1949) examined 
Cerithidea calif ornica collected at Newport Bay, 
California, between October, 1947, and May, 
1949. They found 21 per cent of the snails 
infected with furcocercous cercariae. They 
described one of the latter with 16 flame cells 
but did not describe the cercaria of Mesospepha- 
nus appendiculatus. 
SUMMARY 
The life cycle of Mesostephanus appendicu- 
latus (Ciurea, 1916) Lutz, 1935 has been dem- 
onstrated experimentally. Sporocysts and cer- 
cariae develop in the brackish-water snail, Ceri- 
thidea calif ornica Haldeman, collected at New- 
281 
port Bay, California. The cercaria is furcocer- 
cous and has a flame-cell pattern expressed by 
the formula 2 [(3 + 3 + 3) + (3 + 3+ (3)3 
= 36. Second intermediate hosts are Fundulus 
parvipinnis parvipinnis (Girard) and Gillich- 
thys mirahilis Cooper. Experimentally infected 
fish were fed to hatchery-raised chicks. After a 
lapse of 9 days, egg-bearing worms were re- 
moved from the small intestines of the chicks. 
REFERENCES 
Caballero, E., R. G. Grocott, and Zere- 
cero y D., C. 1954. Helmintos de la Repub- 
lica de Panama, IX. Algunos Trematodos de 
Aves marinas del Oceano Pacifico de Norte. 
An. Inst. Biol. Mex. 24: 391-414. 
Ciurea, I. 1916. Prohemistomum appendicula- 
tum eine neue Holostomidien-Art aus Hun- 
den- und Katzen-darm, dessen Infektion- 
squelle in den Siisswasserfischen zu suchen ist. 
Z. Infektkr. 17: 309-328. 
Dubois, G. 1938. Monographie des Strigeida 
(Trematoda). Mem. Soc. Neuchatel. Sci. Nat. 
6: 1-535. 
1953. Systematique des Strigeida. Mem. 
Soc. Neuchatel. Sci. Nat. 8: 1-141. 
Lutz, A. 1935. Observances e consideranoes 
sobre Cyathocotylineas e Prohemistomineas. 
Mem. Inst. Osw. Cruz 30: 157-168. 
Maxon, M. G., and W. E, Pequegnat. 1949. 
Cercariae from Upper Newport Bay. J. Ent. 
Zool. 41: 30-55. 
Prendel, A. R. 1930. Ein Beitrag zum Studium 
der Helminthenfauna der Hunde in der U. 
d. S.S.R. (Siidliche Ukraine). Zool. Anz. 89: 
323-326. 
Price, E. W. 1928. The occurrence of Prohem- 
istomum appendiculatum in the United 
States. J. Parasit. 15: 68. 
Vernberg, W. B. 1952. Studies on the trema- 
tode family Cyathocotylidae Poche, 1926, 
with description of a new species of Holo- 
stephanus from fish and the life history of 
Prohemistomum chandleri sp. nov. J. Parasit. 
38: 327-340. 
