RODENTJA GEOMYTNAE GEOMYS. 371 



finer one near the inner edge ; (in Thomomys the large central groove is wanting, leaving the 

 fine internal one.) The upper incisors are much curved, and describe nearly a full semicircle 

 passing round almost to the base of the root of the anterior molar. In the lower jaw the arc is 

 also about a semicircle, reaching 4o the side of the base of the condyloid process. 



The upper molars are considerably convergent anteriorly, their inner lines intersecting (if 

 produced) in the incisive foramina. They are all rootless, and diverging widely at their bases ; 

 the anterior is inserted very obliquely forward, at an angle of about 45 with the axis of the 

 skull ; the others more and more near to the perpendicular, and curved, the convexity anterior, 

 yet without becoming quite perpendicular. The lower molars are equally oblique, except that 

 here the posterior is most inclined, and that backwards ; in fact, in its curvature it stands quite 

 parallel to the incisor. The anterior upper molar consists of two regular ellipses, much elongated 

 transversely, of about equal size, and connected by a narrow isthmus which crosses between their 

 middle portions, or a little interior to this ; the second and third molars succeeding are simple 

 ellipses, of nearly equal size the second rather largest, the third about equal to the ellipses of 

 the first ; the last molar is longer, and irregularly three, four, or five sided. The crowns of 

 the first lower molars show, also, the two ellipses, the anterior smallest, the bridge at about 

 the centre ; the remaining teeth are also elliptical, the posterior one narrowest. 



In the skeleton of Geomys, (G. bursarius, No. 1760,) we find the limbs, though short, to be 

 quite massive, the anterior indeed appreciably stouter than the posterior. The vertebral 

 column is short, but the component vertebrae broad and firmly knit together. The neck is very 

 short, its seven component vertebras measuring only about T 3 g- the length of the skull. The 

 second cervical vertebra is large and massive, with a compressed short upper spinous process. 

 The vertebral formula is 7 cervical, 12 dorsal, 7 lumbar, 5 sacral, and 17 caudal. The posterior 

 two sacral vertebrae have their transverse processes anchylosed and expanded so as to come into 

 firm union with the ossa innominata, leaving a wide foramen on each side of the spine, between 

 this junction with the sacrum and that anterior to it, in which the first and second sacral are 

 involved. The bones of the fore leg are stouter than the hinder. The olecranon process is 

 much lengthened, its projection behind the centre of the joint being nearly one-third the whole 

 length of the ulna. The clavicles are well developed. The tibia and fibula are united a little 

 below the middle of the former, and diverge widely above. 



The species of Geomys are confined to the regions east of the Rocky mountains, and, in fact, 

 have not yet been observed much west of the Mississippi, or near the mountains. They are 

 very abundant in Missouri, Iowa, and southern and western Illinois ; they exist also in Texas 

 and all the Gulf States. Florida and Georgia also possess one, possibly two, species, but none 

 have yet been found on the Atlantic coast north of the Savannah river. Southward they reach 

 into Mexico, and, possibly, as far as Central America. 



The species are termed " gophers" in the west, but in Georgia and Florida they are almost 

 universally called " salamanders." Where this latter name is prevalent the term " gopher" 

 is equally well understood to mean the large land tortoise, Testudo polyphemus, to which the 

 Savannah river also serves as a barrier. When either of these names is used, therefore, by any 

 individual, it becomes necessary first to ascertain his region of country before it can be told 

 whether a mammal or reptile is in question. 



From the list of synonymes at the head of this article it will be seen that many genera have 

 been proposed for the gophers. The first, in point of date, is Diplostoma, of Rafinesque, based 

 on reported characters of the Missouri species. With several accurate indications, we are told 



