1894. PROCEEDINGS OF THE NATIONAL MUSEUM. 585 



plates, and the variegated markings of tlie carapace. Texas specimens 

 are somewhat stouter and more compact, and ofteu individuals possess- 

 ing- no color markings are found, but, uotwithstanding- these exceptions, 

 the species is remarkably constant throughout its range. It occupies a 

 larger territory than all other species combined. 



In the taxonomy of Terrapene, as first noted by Dr. Banr, the modifi- 

 cation of the zygomatic arch occupies au important i)osition. The 

 quadrato-jugal is well developed in primitive forms of the genus, rudi- 

 mentary in intermediate forms, 

 and absent in T. ornata, the most 

 specialized species. 



The skull of a species belonging 

 to a closely related genus, Cy- 

 clemmys amhoinensls., is represented 

 in fig. 1. In this species the elon- 



Fio- 1 



gated quadrato-jugal {h) lies along 



the anterior border of the quad- '''^^'' °^ cyclemmys amboinensis. 



rate completely separating the a—postfrontai. 6.-Quadrato-jugai. c.-jugai. 



latter, as well as the squamosal, 



from the jugal (c) and postfrontal {a). The postfrontal is much elon- 

 gated and widened, and with the jugal and quadrato-jugal forms a 

 complete zygomatic arch. 



Fig. 2 shows the zygomatic arch of T. 7najor. The postfrontal has 

 retreated and in this species forms a narrow club-shaped bone just 

 posterior to the orbit and takes no part in the formation of the zygo- 

 matic arch. However, a complete arch is present, composed of the 

 somewhat quadrangular quadrato-jugal and the jugal. 



Fig. 3 illustrates the structure of the zygomatic arch of T. bauri, a 

 form, in this respect, closely related to T. major. It will be noticed 

 that this arch is more slender than in T. major. 



In T. Carolina (fig. 4) the quadrato-jugal is rudimentary and is not 

 connected with the jugal, and hence the bony zygomatic arch is incom- 

 plete. 



In T. mexicana (fig. 5) the zygomatic arch is incomplete, and the 

 quadrato jugal has been reduced to a very small remnant. The same 

 thing may be said of T. friunguis (fig. G), except that in this species 

 the quadrato-jugal is more nearly triangular. In T. ornata (fig. 7) the 

 zygomatic arch has completely disappeared. 



In this connection the modification of the phalanges seems worthy of 

 our attention. In all species there are five digits in each foot, and on 

 the forefoot of each there are five well-developed claws. However, in 

 the fore foot the number of phalanges varies, the number being in 

 T. major, T. bauri, and usually T. Carolina, 2-3-3-3-2; in T. mexicana, 

 T. Iriunguis, and sometimes T. Carolina, 2-3-3-2-2, and in T. ornata, 

 2-L>-2-2-2. 



The hind foot of T. major, T. Carolina, and T. ornata possesses four 

 claws, while in the remaining species but three claws are present. With 



