SACCOMYIDJE-BUDFA-MILY PEKOGNATUIDIN^. 



495 



a third sublamily. In such case, sonu: few of the characters of the three 

 would be as follows : — 



DiPODOMYiN^. — Molars rootless ; upper incisors compressed, sulcate 

 Temporal region enormously inflated. Pelage comparatively soft. 



PERCKiSATHiDiNA;. — Molars rooted ; upper incisors compressed, sulcate. 

 Temporal region moderately inflated. Pelage comparatively hispid. 



Het£ROmyin.£. — Mohxrs rooted ; upper incisors broad, smooth. Tem- 

 poral region "not inflated". Pelage "mixed with flattened spines". 



Subfamily PEllOGNATHIDTN^. 



■= PerognaUat (g«tiDi>), of AL'TIIOItti. 



s= PengMatkidima, Coce^, Proc. Pliilii. Acud. lt)7'>, S78. 



The characters of the group having been already sufficiently elucidated, 

 it remains to note the two genera by which it is represented in North Amer- 



357-359) a mote satisfactory accoDnt of the cburoctvr^of tho genus tbau I have seen elsewhere. As this 

 aoeoani fomisbe* importaot infurmation iiertinont to tho general sabjcct, I transcribe his diagnosis of 

 the geous, and give a version of those portions of the description of the species which tend to further 

 elucidate the generic characters. 



" Deatfs iodiiiTi pagina antica laevigali exserti, molares ^ complicati radicati ; labrnm integmui; 

 rictus pefparros ; n»tmm prominens, rhinario undo ; sacculi buvcules externl piloai ; auriculae mediocres ; 

 Tellug aetcMam, setis lanceolatis, caualiculatis; pedes penta<lactyli ; cnudu annulata, brevipilosa. Os 

 ioterparietale latum, tempora non infiata. 



" Habitos of Mtu. Tbamb prominent, with rounded nail, shorter than the other digits, which run 

 5tb, 2d, 4th, and 3d, the latter longest. Relative lengths of the digits of the bind foot as in lumnB ; Gth 

 but little longer than 1st, 3d longest ; claws rather longer than those of the fore foot, that of the 2d toe 

 longest, couTex on the inner side, flat on tho outer. Sules naked, with the usual tubercles. Incisors 

 compressed, the horizontal croxa-scction triangular, with rounded hinder ongle, and apparently broader 

 than long. Molar series parallel ; lost molur in oacb jaw smallest ; Sid and 3d upper molars of equal size 

 and notably sataller than the Ist ; anterior molar of lower jaw but little larger than the next two .... 



** Inciaors yellow, the lower paler colored than the upper. Anterior superior molar with three 

 separate enamel-tubes — an anterior, longer and uarruwer, a posterior shorter and broader, and a third 

 mach smaller oral one on the inner side of the tooth in a recess where the other two stand apart ; 

 seeond upper molar with a deep internal and slight external emargination, or fold of enamel ; third with 

 a slight exterior emargination, which is either contionons with a transversely-elliptical interior island 

 of enamel, tbn« forming a deep enamel-fold, or else only just roaches this island without fasing with it ; 

 back upper molar with the enamel-pattoru like that of tho socoud ouo, but the posterior half of the 

 tooth ooDsiderably smaller than the anterior portion. 



"Anterior inferior mjlar with two enamel-tubes, tho auterior of which, Humewhat smaller than 

 tjie other, is emarginate before and behind ; the three following teeth with a deep inner and alight outer 

 emargination, as on the upper teeth, which are cither separated or fused together, in which latter case 

 two separale enamel-tnbes result. 



"Tbe rostral portion of tho skull in narrow ; the nasal bones and intermaxillaries project beyond 

 the iuciaan as in allied genera, and tho intermaxillaries form anteriorly a sharp perpendicular ridge. 

 The sttiictiire of the small incisive foramina, the shape of the lachrymal bones and infraorbital foramina 

 are quite as in Gtomf. The latter are wholly in the superior maxillary and are separate from the 

 naaal cavitjr. Since, however, the bony septum is in this case extremely thin , and easily mutilated, the 

 deceptive appearance of communication between the infraorbital foramina and the nasal passages may 

 be aceidenlally produced. The frontal boue,aH in Mu», formsa sharp supraorbital ridge, which continues 

 on to the parietal, thas forming with its fellow of tho opposite side the bonndnry of a level area, with 

 which the inltrparietal, twice as broad as long, is posteriorly continuous, whilst the temporal fossa is 

 excavated [a stioog character uf //c(«iomyiii<z— there is no such formation in Pirog«atk.dince. — ^Tii.]. 1 ho 

 lower jaw strongly resembles that of Perognalhu» in the form of the coronoid process and mandibular 

 angle; the deep pit which is fnu'id in Ommiie to the outer side of tho posterior molar is here waiitiug." 



