NO. 225S TAENIOID CESTODES OF DOGS AND CATS— HALL. 39 



called for the presence of the customary double crown of hooks, he 

 described this form as a new species. If von Linstow's material is to 

 be regarded as actually representative of the normal morphology of 

 the species to which it belongs, then it should be given generic or sub- 

 generic rank on the basis of the single crown of hooks, which is, if 

 anything, more striking than the entire absence of hooks in Taenia- 

 rhynchus saginatus, T. o,f7'icanus, etc., since the causes which might 

 operate to abolish one row of hooks in the genus Taenia s. s. might 

 reasonably be expected to abolish an intercalated row at the same 

 time. It has not seemed advisable to create a new genus for this 

 species for the reason that new data should be added in confirmation 

 of the idea that the conditions reported were normal. It is not an 

 uncommon thing to find specimens of tapeworm in which all the 

 hooks are missing. It sometimes happens that a single row is miss- 

 ing, and the writer (Hall, 1910) reported the loss of the large hooks 

 as a common feature of Taenia halaniceps. In both cases, whether 

 one or both rows of hooks are missing, it appears to be usually the 

 result of trauma. What the nature of this traumatic injury may be 

 is uncertain, but even in mounting specimens hooks will occasionally 

 be detached. Eailliet (1893) has noted that Leidy has described a 

 specimen of Taenia pisiformis provided with a single circlet of hooks 

 (variety a monostephana Diesing), that Bremser has described one 

 without hooks (variety ^ astephana Diesing), and states in comment 

 that these facts are not important and that they deal with material 

 carelessly collected, or very old, or deteriorated material. There are, 

 therefore, grounds for suspecting that the presence of a single row 

 of hooks may be deemed accidental. It may be urged that there is 

 correlated with this an unusual hook shape, consisting of a consider- 

 able reduction of the handle. This condition differs only in degree 

 from that in other tapeworms where the handle is short and stubby. 

 Without regarding it as at all impossible that T. monostephanos may 

 prove to have a single row of hooks as a normal structure, the possi- 

 bility that this may not prove to be the case makes it advisable to 

 leave the matter as it stands and wait for further data. 



The reason for including this species in a paper on the tapeworms 

 of North America is that we have probably more information about 

 the tapeworms of the lynxes than of any other of our wild North 

 American carnivores, and a note of parasites found in other conti- 

 nents serves to aid in securing a really adequate study of the para- 

 sites of our native species. 



Genus MULTICEPS Goeze, 1782a. 



Rynonyms. — Taenia Linnaeus, 1758a, part; Cerehrina Acharius, 

 1782 ; Hydatigena Goeze, l782o, of Batsch, 1786a ; Vesicaria Schrank, 



