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PROCEEDINGS OF THE NATIONAL MUSEUM 



VOL. S3 



There are six vertebrals in the type, and since this number is 

 present in a second specimen (U.S.N.M. no. 12978), it apparently 

 indicates it to be a constant character of this species, as in Baena 

 hatcheri and Chistemon undatum. This extra vertebral has not 

 been found in either B. fulchra or B. alhei'tensis. 



The three anterior vertebral scutes are relatively narrow for a 

 baenid. The first vertebral is shorter than broad, whereas in B. 

 'pulclira it is nearly twice as broad as long, and in B. albertensis 

 these dimensions are subequal. The form of the scutes is clearly 

 shown in figure 9, and their dimensions are given in table 2. 



The sixth vertebral is 

 excluded from the poste- 

 rior border by the inter- 

 vention of supracaudal 

 scutes, as in Thescelus. 

 These two genera are the 

 only baenids in which this 

 vertebral does not extend 

 to the border. 



The plastron has a 

 length at the center of 398 

 mm and a greatest width 

 of about 280 mm. The 

 bridge has a width fore 

 and aft of 188 mm. The 

 anterior lobe is 116 mm 

 long and 143 mm wide at 

 the base. Tlie width di- 

 minishes gradually toward 

 the front, the end being 

 broadly rounded. The 

 posterior lobe is 98 mm 

 long and 134 mm wide at 

 the base. The borders 

 rapidly converge as far 

 back as the anal-femoral 

 sulcus ; from tliis point bacward to the end the sides are nearly par- 

 allel. The posterior end is broadly but shallowly notched at the 

 middle. 



Figure 10. — Plastron of Borcmys grandis. Type. 

 U.S.N.M. no. 12979. ah. Abdominal scute ; an, 

 anal scute ; epi, epiplastron ; /em, femoral 

 scute ; g, gular ; hum, humeral ; hyo, liyoplas- 

 tron ; hypo, hypoplastron ; ing, intorgular scute; 

 in.m, intermarginal scute; tneao, mesoplastron ; 

 pec, pectoral scute ; xiph, xiphiplastron. One- 

 sixth natural size. 



