25 



introduce either genus or species in the body of his work, though 

 in the introductory list lie gives Synaptomy^ as a subgenus of 

 Myodea and catalogues a species, S. cooperi. Tliougli defined with 

 precision, as far as the material would allow, the genus remains 

 little known. I can indorse it unequivocally^, and add all details 

 hitherto "wanting. There is probably' no more strongly marked 

 genus of Arvicolinse. 



Thegrooveof the upper incisor is deep, distinct, and runs near the 

 outer edge instead of along the middle (as in Ochetodon and Reith.ro- 

 don). The incisors are short, broad, and much curved ; their front 

 much bevelled off, so that, viewed in profile, one part of each incisor 

 stands in front of and parallel with the part on the other side of the 

 groove. These teeth tend to the Myodes pattern further in being 

 enamel tubes not completely filled with dentine (calling to mind 

 an unfinished quill pen, after the first oblique slice is cut awa}') ; 

 their tips are not straightly transverse, and generally nicked at 

 the end of the groove. The under incisors, exactly as in 3fyodes, 

 stop as to their roots abruptly just in front and inside of the last 

 lower molar; while in all other Armcolinse I have examined, ex- 

 cepting Myodes and Ciinicu/us, the root runs past (outside) the 

 lower molar up the ramus of the jaw to near the cond3de, this 

 passage of the root making an obvious ridge, here wanting. In 

 Synapfomys, as in the genera just mentioned, the whole condylar 

 ramus is thus flat, with its inner surface nearly plane, separated 

 bj' a strong sulcus from the end of tiie alveolar portion of the jaw. 



As is well known, the molars of Myodes (restricted to exclude 

 Ciiniculus)^ though essentially aggregated rootless prisms as in 

 other Armcoliiise^ are quite different in their details of pattern. 

 Not to go here into detail, I may simply say, that the inner mar- 

 gin of the molar series is crenafe, not sliarpl}' serrate like the 

 outer as in Arvicola. Now this pattern of Myodes is duplicated 

 in Synoptomys^ and so is every other molar detail. Incisors aside, 

 the skull and teeth of Synaptomys are not distinguishable with 

 certainty' from those of Myodes. Outside, Synaptomys is not a 

 lemming, but an Arvicola.^ one, too, with ears as large as in Evo- 

 tomys. An alcoholic specimen might be mistaken at first sight 

 for Armcola ausferus. One might suppose it originally a lem- 

 ming, stranded in time long past in latitude so low as to impress 

 upon it ordinary arvicoline exterior characters. 



