362 BULLETIN" 155, UNITED STATES NATIONAL MUSEUM 



becomes attenuate below the middle of the humerus and finally passes 

 on as a very slender tendon 5 millimeters in length that as usual 

 inserts on the ectepicondylar process. The anterior and posterior 

 portions of the M. latissimus dorsi arise far apart and converge but 

 do not meet until after leaving the body to proceed toward their 

 attachment on the humerus. Both are rather slender. In another 

 New World flycatcher, Myiarchus do??iinicensis, the M. latissimus 

 dorsi show the same conformation. In such oscinine species, how- 

 ever, as Vireo virescens and Vireo crassirostris tortugae the deltoid 

 muscles are similar in development to those of Lawrencia nana. The 

 M. latissimi dorsi also have the same overlapping arrangement as 

 that described in Lawrencia. 



The syrinx of Lawrencia nana is of the diacromyodian type. The 

 intrinsic muscles insert on the dorsal and ventral end of the first 

 bronchial semiring. The single pair of extrinsic muscles is very 

 slender. In Vireo -flavifrom the extrinsic muscles are likewise 

 slender and attenuate. The intrinsic muscles are flattened. Dorsally 

 their attachment is to the end of the second bronchial semiring and 

 ventrally to the end of the first semiring. 



For comparison a description of the anisomyodian type of syrinx 

 found in the Tyrannidae is given. In Tyrannus tyrannus the ex- 

 trinsic muscles are cylindrical and in contrast to those in the 

 oscinine birds just described are strong and well developed. The 

 intrinsic muscles form an enlarged rounded mass on either side. 

 From this an elongation is inserted on the dorsal end of the second 

 bronchial semiring alone. The development of these muscles in 

 Tyrannus verticalis is the same. 



The viscera in perching birds at present offer no known points 

 of value for classification but may be described in Lawrencia to com- 

 plete this account. The right lobe of the liver is slightly longer than 

 the left but the two are nearly equal in bulk as the left portion has 

 a somewhat broader lateral extension than the right. A gall 

 bladder is present under the right lobe and there are two hepatic 

 ducts that enter the ascending arm of the duodenum below its an- 

 terior end. The pancreas has a single lobe included in the loop 

 of the duodenum but only loosely attached to the gut. The intes- 

 tine as a whole measures 115 millimeters in length, while the long 

 intestine, extending from the caeca to the anus is 8 millimeters 

 long. The caeca are paired, ear-shaped lobes about 2.5 millimeters 

 in length and 2 millimeters broad that project as rounded, nodular 

 prominences from the sides of the ventral surface of the intestine. 

 The stomach appears strong and muscular. The ventricular por- 

 tion measures 8 millimeters by 10 millimeters. 



In the skull of Lawrencia there is distinct agreement with the 

 vireos in the form of the free end of the vomer which is not incised, 



