NO. 17S0. A NEW CESTODE PARASITE— HALL. 149 



tion of Tsenia halaniceps to other dog tapeworms, and hence the species 

 of Dibothriocejjhalus and Mesocestoides are not given. 



1. Head armed with two slit-like suckers Dibothriocephalus. 



Head armed with four cup-like suckers 2. 



2. Head armed with hooks; genital pores marginal 3. 



Head not armed with hooks 12. 



3. Head small, armed wdth four rows of hooks; two genital pores in each segment, 



one on each side Dipylidium caninum. 



Head armed with two rows of hooks; one genital pore in each segment 4. 



4. Entire body of tapeworm less than 1 centimeter long and with only three or four 



segments Echinococcus granulosus. 



Body at least several centimeters long and with numerous segments 5. 



5. Gravid uterus with branches so numerous and so closely approximated as to give 



the outline of a lobed sac, one lobe often crossing the lateral excretory canal. 



Tsenia halaniceps. 



Gravid uterus forms a system of fairly distinct lateral branches, none of them 



crossing the lateral canal 6. 



6. Large hooks 225 to 250 /i long Tsenia pisiformis. 



Large hooks not over 220 /t long 7. 



7. Mature segments broader than long 8. 



Mature segments longer than broad 9. 



8. Head small, genital pore unusually large and prominent Tsenia krabbei. 



Head large, 1 millimeter broad, genital pore not prominent Tsenia hydatigena. 



9. Guard of small hook twisted so that its flat surface tends to lie in the plane of the 



blade and handle Tsenia brachysoma. 



Guard of small hook not twisted 10. 



10. Adult strobila not over 20 centimeters long; large hooks 95 to 140 n long. 



Taenia brauni. 

 Adult strobila 40 to 100 centimeters long 11. 



11. Large hooks 150 to 170 n long; eggs spherical and 31 to 36 ju in diameter. 



Multiceps multiceps. 

 Large hooks 135 to 156 /« long; eggs ovoid and 33 to 41 p. long by 26 to 31 n wide. 



Multiceps serialis. 



12. Genital pores ventro-median Mesocestoides. 



Genital pores marginal Proteocephalus punicus. 



Tsenia erytliraea has been erroneously included as a tapeworm of the 

 dog by von Linstow (1905); Setti (1897) described it from Canis 

 mesomelas. 



The only tapeworms which the writer has found recorded from the 

 lynx are Tsenia laticollis Rudolphi, Tsenia monostepTianos v. Linstow, 

 and a species of Mesocestoides. Txnia laticollis can readily be dis- 

 tinguished from T. halaniceps from the fact that the former has very 

 large hooks, the smaller ones measuring 128 /j. in length and the 

 larger 239 p., according to von Linstow (1905). Tsenia monostepTianos 

 can readily be distinguished from the fact that it has a single circlet 

 of hooks all of the same size instead of the customary double circlet 

 of large and small hooks. Mesocestoides differs from T. halaniceps 

 in that the head is unarmed and the genital pores are ventro-median, 

 as indicated in the above key. 



