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PROCEEDINGS OF THE NATIONAL MUSEUM 



VOL. S3 



The first vertebral is much shortened, and all are wider than long. 

 The form of the vertebrals is clearly shown in figure 11, and their 

 principal dimensions are given in table 3. 



The fifth vertebral does not come to the posterior edge of the shell, 

 as in the other members of the Baenidae, but is separated from it 

 by paired supracaudal scutes, as in T. imilens. 



The total number of marginal scutes cannot be determined from 

 this specimen. 



The plastron is large. The axillary notch is forward, being only 

 35 mm from the front of the carapace. The opening for the head 

 and fore legs is therefore much restricted. The front lobe extends 



well forward beyond the 

 front of the carapace. The 

 anterior lobe has a length 

 of 89 mm and is shallowly 

 excavated on the mid line. 

 The base is 115 mm wide, 

 but it narrows rapidly to- 

 ward the front, so that at 

 the gular sulci the width 

 is only 74 mm. The poste- 

 rior lobe at the base is 135 

 mm in width. 



Anteroposteriorly t h e 

 bridge has a width of 187 

 mm. From its inner end 

 to the border of the cara- 

 pace it is about 112 mm. 



None of the sutures of 

 the plastron is discernible. 

 The sulci are plainly im- 

 pressed, and most of the 

 scutal areas are well defined, as shown in figure 12. 



No trace of intergular scutes was found, although present in 

 Thescelus insilens Hay. The gulars are large and meet on the mid 

 line for a distance of 28 mm ; the humerals for 61 mm ; the pectorals 

 for 94 mm ; and the abdominals for 44 mm. On the bridge there are 

 four inframarginals that have been satisfactorily determined. The 

 median longitudinal sulcus runs a somewhat irregular course as in 

 many other baenids. 



This species is at once distinguished from the Lance T. {nsilens 

 by the bosslike ornamentation of the carapace, the relatively wider 

 vertebrals, posterior border of carapace without constrictions, and 



Figure 12. — Plastron of Thescelus hemisphcHca. 

 Type. U.S.N.M. no. 12818. ab. Abdominal; 

 fern, femoral; ff, gular; hum, humeral; iti.m, 

 inframarginaLs ; pec, pectoral scute. One- 

 sixth natural size. 



