2 U.S. NATIONAL MUSEUM BULLETIN 2 73 



tations of Alouatta which have permitted this genus to follow its 

 own evolutionary path will become evident. 



Four enb aimed specimens of the red howling monkey (Alouatta 

 seniculus) were dissected under an Aloe Dazor fluorescent lamp with 

 a magnifier head. Three were adult males, two from central (Guarico 

 State) Venezuela, and one from eastern (Delta Amacuro Territory) 

 Venezuela. The adult female was obtained through animal dealers 

 centered in Leticia, Colombia. In addition, the masticatory and 

 palatine muscles on the severed heads of two young adult females 

 and one adult male from central Venezuela were studied. The ventral 

 neck muscles were also observed in this male. It was not possible 

 to observe the facial and dorsal trunk muscles in the female because 

 they had been damaged while removing the brain and spinal cord. 

 In the following account all this information has been pulled together. 

 Variations are indicated wherever present. 



The data are organized according to a sUghtly modified version of 

 a scheme developed by W. L. Straus, Jr. (unpublished), which is 

 based on his own experience and on the previous work of A. B. Howell 

 (1936, 1939). The recently approved Nomina Anatomica (1966) has 

 been employed, but other commonly known anatomical terms have 

 occasionally been used. To facilitate the comparison of the facial 

 musculature of the howler with that of the Atelinae and Cehus, I 

 have adhered to the terminology used by Schreiber (1928) and Huber 

 (1930, 1931, 1933). It was found that some former students called 

 their specimens by names accepted today only as synonyms. These 

 are followed in this text by a parenthesis containing the name which 

 is now accepted. In this work every muscle is first described and 

 comments are added about observations made by other authors on 

 the same structure of Alouatta. This is followed by the innervation 

 and inferences about the function. The latter were based on the top- 

 ographical arrangement and on what is presumed to be the action of 

 the particular muscle in man or other primates (Howell and Straus, 

 1933). Finally, the comparative anatomy is reviewed. Sometimes 

 groups of muscles are treated together in relation to functional and 

 comparative aspects. 



This work is based on the dissertation presented by the author to 

 the Graduate Board of the Johns Hopkins University in partial 

 fulfillment of the requirements for the degree of Doctor of Philosophy, 

 June 1966. It was aided in part by a training grant from the National 

 Institutes of Health. 



I wish to express my appreciation to Dr. W. L. Straus, Jr., De- 

 partment of Anatomy, Johns Hopkins University School of Medicine, 

 for his guidance and indispensable advice, and to Dr. D. Bodian, 

 Chairman of that Department, who arranged for financial support. 



