GO Mcrriam — The LeniDiinr/s of tlic Genus Sjjnajiloinijs. 

 Synaptomys helaletes gossii fjal)S[). iiov. 



Arricold {Si/vaptoriu/s) gdssii Buird MS., Cones, IMond.ir. X. Am. K(x1entia, 

 13. 235, 1S77 {nonien nudum). 



Type localitij. — Neosho Falls, Kansas, No. (JUlo, J" old, U. S. National 

 Museum. Collected by B. F. Goss, 18G(). 



General characters. — Similar to S- hel'ilete-'^, but color probably redder; 

 rostrum longer ; audital bnlhe smaller. 



Color. — Not positively known ; probably more reddish brown than in 

 cooperl or helaletes. The mounted specimen in the National ^Museum has 

 been skinned out of alcohol, and the skins originally collected by Captain 

 Goss cannot be found. 



Cranial and dental characters. — Skull as a whole similar to that of S. hela- 

 letes, but even larger, with rostrum and nasals longer ; zygomata more 

 bowed outward in the middle ; orbital fossse larger ; audital budae smaller ; 

 postpalatal pits deeper, defining a distinct median ridge between them, 

 which ridge projects slightly into the postpalatal notch. Viewed from 

 below, the rostrum and incisive foramina are conspicuously longer. Owing 

 to the small size of the audital bulla', the sides of the basioccipital are 

 less deeply excavated, and the vacuity on each side of the basisphenoid 

 is much larger than in helaletes; the incisors are very broad and heavy, as 

 in helaletes, and the molars nearly as large (the upper series measuring 7 

 mm.). 



3feasHrements. — Average of 6 specimens from type locality : total length, 

 120; tail vei'tebne, 20.5; hind foot, 19.* 



Subgenus :\IICTOMYS True. 



A new and exceedingly interesting leniniing-vole from Ungava, 

 Labrador, was described by Mr. F. W. True, in 1894, under the 

 name Midomys innuitus. On comparing the type specimen of 

 this species and specimens of the two related species liere de- 

 scribed, with Synaptomys cooperi, it ap})ears that the most im- 

 portant character separating Mictomys from Synaptomys is the 

 absence of closed triangles or enamel loops on tlie outer side of 

 the lower molars (Fig. 1). In addition, the upper incisors in 

 Midomys are more slender and much paler in color, and the part 

 exterior to the sulcus is nearly white, while in Synaptomys the 

 whole enamel face is deep orange. The chief cranial differences 

 are in the post-palatal region. In Midom.ys there is a distinct 

 median az^'gos ridge not present in Synaptomys,^ where the 



*Hind foot from alcoholics; the other measurements taken in flesh by 

 Captain Goss and converted from Cones' table, N. Am. Rodentia, p. 23(), 

 1877. 



t Kxcept in .S'. c/ns-s// in which the jiost-indatal pits are so deep that the 

 median part of the palate between them is left as a nearly vertical pro- 

 jection comparable to, but much shorter than, that of Mictontijs. 



