ZAPODlDiH— ZAPD8 1IUDSONIU8— KXTEUNAL CUAUACTKllS. 473 



grcntly oxceods that of llin iMxIy ; n pociiliiir (•ondition Of tlio oxtcrnni cnr; 

 nnd a pli^sid^fiiomy (|iiite Wko. tlmt iif the Sacromt/ida. There are also well- 

 (levclciped iiitertinl cli('ck-|i()iiches, shared, in a less degree however, by vnriuus 

 Aiiierican Muridce* These pouches, as well as eaii he judged from alcoholic 

 specimens, are leliitively nhout as large as those of Tamiax I'or iustnnce. 



The l)ody of Xnjiu.t is large l)ehiii<l, in co-rolatiou with the greatly-devel- 

 oped posterior limbs, and tapers to the fore in n . 'gidar manner; the head 

 being comparatively sinidl, and there being no noticeai)le constriction of the 

 neck. The head is conoidal, with a prominent and rather blunt snout and 

 retreating under jaw. The rather snudl eye is midway i)etween the nose and 

 ear. The upper lip is not visibly cleft, and is densely hirsute, with ii fringe 

 of hairs d<;peiiding over and almost hiding the small front teeth. The naked 

 muffle is of rather small size, and entirely inferior in position; above it, the 

 hairy skin crosses "with n deep transverse crease, forming a sort of imperfect 

 overhanging flap, which is freely movable l)ack and forth, even in alcoholic 

 specimens, and looks as if it might be drawn down to partially cover the nos- 

 trils. (I have observed much the same thing in Saccomj/irfa.) The nose-pad 

 is impressed with a pair of median vertical grooves, aiul a transverse one is 

 seen in some cases. The nostrils are completely lateral in position. The 

 whiskers are rather sparse, but some of them are nearly half as long as the 

 body. 



The structure of the external car is rather remarkable (among Rodents) 

 for the provision for perfect closure of the meatus, as in the Soricida for 

 instance. The antitragus develops into a great flap, completely reversible, 

 and capable of being applied against the meatus ; and such, in fact, appears 

 to be its usual position. The tragus, likewise, expands into a wide frill, or 

 thin, free, rounded border, which ordinarily lies in apposition with the anti- 

 tragal lobe opposite, completing the closure of the ear. On turning over 

 these two flaps, the vestibule of the ear is seen to be of unusually large 

 dimensions. The conch itself is of an ordinary contour, coming to a blunt 



* Tlio preaonce uf chiMtk-puiicbeii in the geuiiB netfenmij/t was first noted in 1830 by Gapper, who 

 Tef»iTed BiiociineDi) of the common Haperomgn leucoput to Cricetut ou tbm tccoupt, ' ' t:iIj:i-,kiD)( a species 

 C. m^auio. In this matter, he was sncceodcil by Bbini in 1857, who uliio ruougnized the pouches, and 

 endorsed a Haperomyt myoidn mainly n|)on this featnre, failing, however, to observe that they also 

 existed in other species uf the same genua. At the same time that Mr. J. A. Alien announced the before 

 unknown pouches of Zapiit hudioxiiu, ho hIso showed that they occurred as well in various species of 

 Utiptromy ; and my subsequent cliosections have satisfied me that pouches are present in all the North 

 Aiuerlaiin H|iaci«s of Beiperomyt proper ; <. e., the subgenus yetperimut as established by mc : Pruc. Acad. 

 Mat. Sei. I'hila. 1S74, 17d. 



