ART. 17 NEW LARVAL NEMATODES SCHWARTZ 7 



forms described by the present writer have a well-developed intes- 

 tinal cecum, they also have a conspicuous ventriculus, and are there- 

 fore probably not identical with Porrocaecuni retlculatum. How- 

 ever, as already stated elsewhere in this paper, the immaturity of 

 the present writer's specimens does not warrant comparison with 

 any known adult forms. 



The determination of the adult stages of P orrocaecumh encapsu- 

 latwn and Porrocaecum amencanum must await the examination of 

 probable definite bird hosts in the vicinity of the District of Co- 

 lumbia and Virginia for parasites of the digestive tract, and the 

 experimental infection of birds with Porrocaecum as a result of 

 feeding them encysted larvae from intermediate hosts. 



SUMMARY 



Two encysted larval nematodes occurring in Insectivora are de- 

 scribed for the first time from the United States, and are definitely 

 shown to belong to the genus Porrocaeciim. These forms appear to 

 be related to encysted nematodes described from moles and shrews 

 in Europe under the name Ascaris incisa and under other names, 

 but are distinct from the European fonns as regards location in 

 the host as well as regards certain morphological character. 

 Porrocaecum encapsulatum described in this paper from the shrew 

 {BlaHna hrevicauda) is strikingly larger than any of the related 

 forms heretofore known, and PorrocaecuDi amerlcanum from the 

 mole (Scalojms aquaticus) though agreeing in size with Ascaris 

 incisa is considered distinct, because the latter is probably a group 

 name and has been incompletely described, so that there exists no 

 definite basis on which to make morphological comparisons, 



The adult forms of the larvae here described {Porrocaecum encap- 

 sulatum and Porrocaecum amerlcanum) probably occur in birds of 

 prey, such as hawks and owls. Owing to the incomplete state of 

 development of these larvae, particularly as regards the mouth parts, 

 it is impossible to compare them to any advantage with adult speci- 

 mens of Porrocaecum collected from American birds of prey. The 

 ultimate solution of the question of the adult stages of the larvae 

 described in this paper will have to be based on more complete 

 knowledge of the species of Porrocaecmn that occur in American 

 birds of pre}^ and on feeding experiments. 



REFERENCES TO LITERATURE CITED 

 Bayxis, H. a, 



1920. — On the classification of the Ascaridae. 1. The systematic value of 

 certain characters of the alimentary canal, Parasitology, Cambridge 

 [Eng.], vol. 12, ser. 3, Sept., pp. 253-2G4, figs. 1-6. 

 1924. — Some considerations on the host-distx'ibution of parasitic nema- 

 todes, Linnean Soc. Journ.,-Zool., vol. 36, April, pp. 13-23. 



