170 U.S. NATIONAL MUSEUM BULLETIN 2 75 



dark-colored basally and pale-colored distally; vibrissae relatively 

 long, formed from both light and dark-colored individual hairs, and 

 extending well beyond the level of the ears ; tail relatively long, dorsal 

 surface about same color as dorsum, but more heavily suffused with 

 black, and ventral surface uniformly Pinkish Buff; prominent black 

 pencil occupies terminal one-third of the dorsal surface of the tail and 

 extends along the ventral surface one-half this distance. Skull : Medium 

 in size; auditory bullae markedly inflated both laterally and ventrally ; 

 lateral meatal expansion large and applied to squamous part of the 

 temporal bone; suprameatal triangle small, elliptical, and completely 

 enclosed by enveloping processes of the temporal and supraoccipital ; 

 anterior portion of basioccipital and body of basisphenoid reduced to 

 narrow rod-shaped structures between the large bullae. 



Comparisons. From topotypes of Meriones caudatus luridus, a 

 single topotype of Meriones caudatus caudatus, 302246, from Bir 

 Fergian, and near topotypes of M. c. caudatus from near Hun, Derg, 

 and Bir Allagh, Tripolitania, differ in having dorsal pelage more 

 heavily suffused with black, shorter tails with more prominent pencils 

 (black rather than brownish) and being significantly smaller in all 

 cranial measurements except the length of the upper molariform 

 toothrow. 



When representatives of M. c. caudatus are compared with topotypes 

 of Meriones caudatus confalonierii, the latter differs in slightly paler 

 color of the dorsum and slightly smaller size of most cranial characters, 

 being comparable in least interorbital breadth and width of rostrum. 

 In general body size animals of the two subspecies are almost in- 

 distinguishable. Although the above characters are somewhat tenuous, 

 and M. c. confalonierii is poorly defined morphologically, the dif- 

 ferences are still sufficient for separating subspecies, and I prefer to 

 regard M. c. confalonierii as a valid form. 



For comparison with M. c. amplus, see account of that subspecies. 



Remarks. A single topotype, 302246, from Bir Fergian, 10 kilo- 

 meters south of Socna, Tripolitania, agrees closely in external measure- 

 ments and color with the original description of Meriones libycus 

 caudatus Thomas (1919, p. 267). Unfortunately, the skull of this 

 single topotype was inadvertently lost, and cranial comparisons are 

 not possible. Cranial measurements of representative series from 

 nearby localities are decidedly smaller than those of the type specimen. 

 I have not examined the type specimen of Meriones libycus caudatus 

 (= Meriones caudatus caudatus), but judging from the literature, 

 probably it represents an extremely old and outsized male which is 

 not entirely representative of this subspecies. 



The various populations of this subspecies in Tripolitania are rather 

 uniform in cranial characters, but some local variation is present in 



