448 
ZOOLOGY OF 
9. Callithrix torquatus {amictus, Geoff.) ; Upper Rio 
Negro. 
10. Cain thrix per sonatuSy Geoff. ; south bank of Upper 
Amazon. 
11. Nyctipithecus triviryatus, Humb. ; Upper Rio 
Negro. 
12. Nyctipithecus felinus, Spix ; Upper Amazon. 
13. Pithecia irrorata {Jiirsuta, Spix); south bank of 
Upper Amazon. 
14. Pithecia — — , north of Upper Amazon. 
15. PracMurus satanas^ Br. Mus.; Guiana, east bank 
of Rio Negro. 
16. BracJiiurus oakary, Spix; Upper Rio Negro. 
17. PracMurus ruhicundus, Isid.; Upper Amazon. 
18. PracMurus — , south side of Upper Amazon. 
19. JaccJius hicolor, Spix; north of the Amazon and 
Rio Negro. 
20. Jacchus tamarin, Br. Mus.; Para. 
21. JaccJius n.s., Upper Rio Negro. 
Of the above, the first seven have prehensile tails, a 
character only found among the monkeys of America. 
The hoAvlers, forming the genus Mycetes, are the largest 
and most powerful. They have a bony vessel situated 
beneath the chin, and a strong muscular apparatus in 
the throat, which assists in producing the loud rolling 
noise from which they derive their name, and which ap- 
pears as if a great number of animals were crying in 
concert. This however is not the case ; a full-grown 
male alone makes the howling, which is generally heard 
at night, or on the approach of rain. 
