ART. 17 NEW LAEVAL NEMATODES SCHWARTZ 5 



tightly coiled, the comparatively large number of coils filling the 

 cyst completely, whereas Ascaris incisa assumes the shape of the 

 figure 6 or 8 within the cyst, the interior of the latter being but 

 partially filled by the parasite. Ascaris acanthura has a shape more 

 or less resembling the figure 8, and only partially fills the cyst, so 

 far as can be judged from Leuckart's figure. The species from the 

 mole described in this paper {Porrocaecimi amencamim) is similar 

 in size to Ascaris incisa, but in vieM' of the fact that the latter ap- 

 pears to be a group name, and that a precise account of its morph- 

 ology has not been published, it is inore desirable; not to add to the 

 already existing confusion, and accordingly the form from the 

 American mole {Scalopus aquaticus) may best be considered dis- 

 tinct from that from the European mole {Talpa europaea). 



THE GENUS PORROCAECUM RAILLIET AND HENRY 1912 



The genus Porrocaecum is included in the family Ascaridae, and 

 according to a recent revision of this family by Baylis (1920), it is 

 assigned to the subfamily Anisikinae Kailliet and Henry, 1921, 

 emended by Baylis, 1920. Baylis defines the genus Porrocaecum as 

 follows : " Esophagus 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 cecum present. No eso- 

 phageal appendix. Interlabia present, usually small dentigerous 

 ridges present." Fifteen species belonging to this genus are listed 

 in the catalogue of the Zoological Division of the Bureau of Animal 

 Industry, the hosts being fishes, amphibia, birds, and marine mam- 

 mals. At least one species {Porrocaecum crassum) is probably of 

 economic importance, since it occurs in ducks. It is not improbable 

 that further investigations will add to the number of species of 

 Porrocaecum on the one hand and subtract from it on the other 

 hand. Only five species listed under this genus are regarded by 

 Baylis (1920) as probably belonging to it, while the same writer 

 regards certain species from fish with a type of alimentary canal 

 characteristic of the genus, but not as yet included in it, as requiring 

 further investigation. It may be concluded, therefore, that our 

 knowledge of the genus is as yet incomplete, and that further investi- 

 gation will probably result in bringing to light additional species 

 which may lead to a new conception regarding the affinities of the 

 various members noAv included in it. 



^ LIFE HISTORY OF SPECIES OF PORROCAECUM 



Our present knowledge of the life history of species of Porro- 

 caecum is very fragmentary, the essential facts being understood in 

 only two species, so far as the present writer has been able to ascer* 



